In his 1726 fiction, Gulliver’s Travels, Jonathan Swift sends his hero, following the better-known sojourn in Lilliput, to a land of giants, in comparison with whom he is now as small as the Lilliputians had been to him. The king of this land is perplexed as to the origins of this “homunculus” and appoints his greatest scholars to conduct an inquiry. “They all agreed,” the narrator relates, “that I could not be produced according to the regular laws of nature, because I was not framed with a capacity of preserving my life.” After much debate, he goes on,
they concluded that I was only relplum scalcath, which is interpreted literally, lusus naturae: a determination exactly agreeable to the modern philosophy of Europe, whose professors, disdaining the old evasion of occult causes, whereby the followers of Aristotle endeavour in vain to disguise their ignorance, have invented this wonderful solution of all difficulties, to the unspeakable advancement of human knowledge.1
While Swift ridicules the idea of lusus naturae, which is interpreted literally, “games of nature,” as having failed to progress beyond premodern theories of the origins and causes of natural forms, in fact he does not quite give an accurate account of contemporary trends in modern philosophy, since by the time he is writing the appeal to games of nature has already largely gone out of fashion. One of its firmest opponents, until just ten years before the publication of Swift’s satire, was none other than Leibniz.
The idea in question enjoyed its greatest currency in the sixteenth and seventeenth centuries and was generally deployed to explain unusual or aberrant productions of nature, not only reports of miniature men but, more commonly, such things as the supposed figures of Jesus or Mary in the side of a cliff or the medical abnormalities reported on by Jacques Bouquet in his letters to Leibniz from Padua (discussed in chapter 1). What is more, it, or a close variant of it, was just as often deployed to account not only for wondrous occurrences, but also for perfectly quotidian cases of the emergence of organic form.
Consider, to begin, the Renaissance Platonist Marsilio Ficino’s vivid account of a number of natural phenomena, including, among other things, spontaneous generation and the influence of the maternal imagination upon the development of traits in the fetus. Ficino asks rhetorically: “From the beginning of any thing that is to be generated, do not celestial influences bestow wonderful gifts in the concoction of the matter and its final coming together?” Spontaneous generation, then, is for him nothing other than what occurs when the rays of the heavens concoct suitably disposed matter into complex organisms. Thus Ficino goes on to ask: “Do not innumerable frogs and similar animals often, when the face of the heavens favors it, leap forth out of the sand in a moment? Such is the power of the heavens in well-disposed material.” Ficino adduces a number of other earthly phenomena that involve the influence of the powers of vision and imagination, making the case that, a fortiori, celestial rays have the power to influence the form of earthly things. He maintains that “the immense size, power, and motion of celestial things brings it about that all the rays of all the stars penetrate in a moment the mass of the earth.” These rays even penetrate all the way to the center of the earth. “By the rays’ intensity, the material of the earth there—being dry and far from any moisture—is immediately kindled and once kindled, is vaporized and dispersed through channels in all directions and blows out both flame and sulfur.” He describes this fire as “very dark,” and “like a flame without light,” using the same vivid phrase that, as we have seen, Descartes would later echo in describing the “fire” that burns in the heart at the moment the fetus is quickened. Ficino continues: “Finally, diverse powers come into being in the combinations of rays with each other of one sort or another, here and there . . . instantly with an emission of rays forces are imprinted in images, and divers forces from a different emission.”2
Consider, in turn, the sixteenth-century Dominican Antoine Goudin’s account of the origins of fossils. In his Philosophy, Following the Principles of Saint Thomas, he argues that there are both efficient and final causes at work in the earth’s production of rocks that resemble animals or parts of animals. Their efficient cause is a sort of cooking brought about by exhalations from the depth of the earth that makes the strata where fossils are found into a furnace of sorts. Their final cause, in turn, is
a certain force earth itself possesses variously, following the different places in which the mixed body is formed. This force, similar to the maternal bosom from which animals arise, assuredly plays a great role in the formation of these bodies; this is why, according to Aristotle and Saint Thomas, earth and water furnish to everything arising from the bowels of the earth their matter and bosom, as would a mother, while heaven and the stars fulfill the office of the father, who imparts the form.3
For Goudin, a male formative principle exercises its influence over the maternal matter of the earth and thereby gives rise to forms in earth that resemble living beings. A fossil is simply a “spontaneously” generated creature whose form is imposed in the wrong sort of material—stone, say, rather than pliable mud—and so is unable to live and move as an animal does, even if it partakes of animal form.
Thus we see that the question of the origins of fossils is intimately connected to the question of spontaneous generation, which in turn is assimilated, by Ficino among many others, to the process of trait acquisition in fetal development. All of these are cases of nature’s productive capacity, which is conceived along the lines of traditional accounts of sexual generation as the imposition of form upon matter. Those instances of this sort of productivity that appear to happen exceptionally—as, for example, in the case of monstrous species, or the appearance of animal-like traits in human infants, or the appearance of organic forms in a geological substratum, as in the case of fossils—are picked out as games of nature, but these are only the most noteworthy instances of a much more diffuse, indeed universal, natural generativity.
One might suppose that mechanist natural philosophers would shy away from the view that nature, in itself, is able to generate any of the things described by Ficino and Goudin. After all, their model of generation had been based on the sort of basic conceptual division between form and matter that the mechanists would come to eschew. Yet, remarkably, the sort of explanations to which these premechanist thinkers appealed continued to play an important role in the seventeenth century in accounting for the causes of the emergence of organic order, whether in a pond, in the side of a cliff, or even in the particular traits of a child’s face. Leibniz, with his firm insistence that “nature does not play,” would perhaps be more successful than any of his predecessors or contemporaries in moving beyond the sort of explanation favored by Ficino. Even Leibniz, however, does not exclude, for example, the power of the faculty of the imagination in embryogenesis, and to the extent that he does succeed in eschewing this and similar powers, interesting problems arise as to the place of spontaneity in Leibniz’s natural philosophy.4
In this chapter we will look at three distinct cases of natural generativity: (i) the influence of the maternal imagination in fetal development, (ii) spontaneous generation, and (iii) the origins of paleontological forms. We will be considering Leibniz’s position in the history of attempts to account for the emergence of organic order in three broad classes of entity: embryos, worms, and fossils. Insofar as these classes are not generally seen today as giving rise to the same kind of questions, in this chapter, more so than in the others, we shall have to stray for long periods from Leibniz and into the broader context of these natural-philosophical questions in order to properly understand the full rationale of Leibniz’s strategies in answering them.
As early as the Directiones of 1671, Leibniz expresses a cautious openness to the possibility of influence of the imagination on the states of the body. He neither accepts it nor rejects it, but instead proposes that “tests should be set up to determine what the powers of the imagination and the belief[s] of the patient are capable of bringing about. To this end physicians should be given the art and the means to convince the patient of all manner of things.”5 He writes more than three decades later in the Nouveaux essais of 1704 with considerably more certainty about the special case of the maternal imagination: “It can happen that a female brings an animal into the world that seems to derive from another species, and that the imagination of the mother alone has caused this irregularity.”6
What now are the reasons for the endurance of interest in this doctrine, dismissed by some scholars as a mere “wives’ tale,”7 in the philosophy of Leibniz? Does it do important work in the context of his theory of generation, or does it occur in his writings, as it were, vestigially? In order to adequately answer this question, it will be useful to consider the role it played in the philosophy of a number of his contemporaries. As we will see, the theory plays a vastly less important role in Leibniz’s thought than in that of other mechanist philosophers, and this, it will be suggested, is for the deep reason that it is incompatible with his doctrine of preestablished harmony.
The imagination theory, while in some sense helping its defenders to avoid the now off-limits forces of Aristotelian natural philosophy, in another sense allows these forces to continue on in a different guise. It might be suggested that the transformation the general account of heredity undergoes from the ancient to the early modern period effectively shadows the better-known transformation of the concept of idea. Just as we witness a transformation of this latter concept—which originally described real entities in the world or beyond it that inform the world and make individual beings the sort of beings they are—into a concept that describes mental entities had by individual thinking subjects in the act of thought, so too we witness a migration of the responsibility for heredity from the form of humanity or bovinity, once thought to direct the individual human or cow fetus’s gestation, to the mother’s own, individual imagination. Indeed, from the Renaissance into the early modern period, the role of the imagination in the inheritance of traits (hereafter, “the imagination theory”) was most often conceptualized as just another causal force in nature rather than a deviation from nature’s ordinary course.8
Interestingly, many sixteenth-century authors appeal to the imagination theory while making a conscious effort to dissociate it from magic. Pietro Pomponazzi claims in his 1567 De naturalium effectuum admirandorum causis (On the Causes of Admirable Natural Effects) that the power of imagination can be used to cure the illnesses of others and implies that it can also be used, should one wish, to bring illness to the healthy. Only the latter goal is pursued by “old sorcerers [vetulis fascinantibus],”9 while the former is just good medical practice. This same distinction between the legitimate imagination theory and the spurious practices of old sorcerers such as chiromancy is sustained into the seventeenth century; as Lynn Thorndike notes, physiognomy, broadly construed in the early modern period to include the imagination theory, “is to be accounted for by the fact that, while other forms of divination, including for many even judicial astrology, were condemned as superstitious, it was regarded as having a natural basis.”10
Even Paracelsus, seldom one to feel the corrective prick of Occam’s razor, seeks to place the imagination theory on a firm and respectable footing relative to other evidently more speculative theories such as judicial astrology. In the De natura rerum of 1537 Paracelsus claims that birth defects are to be attributed to the degree of the zodiac rising on the Eastern horizon at the time of birth: “I have observed many . . . monstrous signs, in men as well as in women, all of which should be regarded as monstrous signs of occult ascendants with evil influence. Hence the proverb: ‘the more crooked, the more wicked; lame limbs, lame deeds.’ For these are signs of vices and seldom signify anything good.” Thus, birth defects are signs of vice, and this vice is traceable to the positions of the stars. But, Paracelsus continues, “Often these monstrous signs come from the stars of people’s minds, which . . . ascend and descend in accordance with the individual’s fantasy, mode of thinking, and imagination. Thus, often women give birth to monsters or to children marked with signs while they are still in the womb, because the women have been subject to fears or terrors, and feed on these in their imagination.”11 For Paracelsus, imagination moves in to explain given effects when astrological explanation seems far-fetched; from his point of view the explanation in terms of the power of the imagination is preferable, in view of its evident naturalism, to the explanation in terms of the power of the stars.
Leibniz, at least in the Directiones of 1671, believes that neither power should be dismissed out of hand, even if both should be subjected to further scrutiny. We have already seen (in chapter 1) his recommendation in that work that tests be set up to determine the power of the imagination upon the body. Elsewhere in the same work, Leibniz advises that “attention should be paid to astrological effects: whether for example it is true what they say, that if a woman gives birth during a (solar) eclipse, she and the child will die, and other things in this sort of tradition.”12
Many premechanist thinkers had been interested in appealing to the power of the imagination over the developing fetus primarily in order to explain games of nature in a narrow sense, that is, instances of abnormal fetal development in which nature is, so to speak, dirempted from its usual course. In the seventeenth century, in contrast, this same power came to be invoked in the course of explaining the ordinary process of trait acquisition and in the course of explaining what happens, as Aristotle says, “always or for the most part.”13 This transformation may be seen in part as the natural consequence of the banishment of final and formal causes from scientific explanation. For an Aristotelian there is an independent formative power guiding the fetus, a power with which the mother’s imagination might interfere; indeed, for Aristotle the mother’s role in reproduction is in a sense always interference, for it is her material causation that impedes the perfect numerical reproduction of the father. In the later Aristotelian tradition, the restriction of the mother’s role to pure material causation recedes, yet the possibility of her imagination playing a formative role is still seen as a deviation from the ordinary course of reproduction. In the Coimbran Aristotle commentaries, the imagination is held to “occasionally [make] the formative faculty wander from its target, and imprints upon the fetus absurd or alien figures.”14 For the Coimbrans there was a proper, innate formative faculty that guided the ordinary development of the fetus, and the mother’s imaginative faculty could, in moments of distress or excitement, interfere with the normal formation of the fetus: the one formative faculty could get in the way of the other one, while the natural process was the development of the new natural being from internal forces. The influence of the external maternal imagination was thus unnatural or aberrant. In mechanist embryology, by contrast, the fetus had no innate formative faculty of its own: it was entirely formed by the impact of external forces, including the maternal imagination, now nominally reconceived as a purely physiological force. In other words, in the sixteenth century, the imagination theory was convenient, primarily in the explanation of aberrations; in the seventeenth century, deprived of formal and final causes in the account of organic growth, it was not so much convenient as necessary in the explanation of the regular course of sexual reproduction.
At least one mechanical natural philosopher, as we will see, would observe that without such a power of the maternal imagination one would not only be unable to account for the inheritance of particular variable traits, one would also be left unable to explain ordinary species reproduction. While mechanists could be reasonably confident that inorganic natural phenomena, and perhaps even “the formation of the fetus in general,” might soon be explained in terms of matter in motion alone, such limited means seemed utterly insufficient when attention was turned to the seemingly irreducibly complex process by which, as Aristotle had put it, like begets like, and a mechanist account of this phenomenon, such as that offered by Descartes, comes out looking like a fantastic exercise in wishful thinking.
For roughly sixteen years, from 1632 to 1648, Descartes appears to have been frustrated by the evident intractability of animal generation and fetal development within the constraints of mechanism. In the Discours de la méthode he acknowledges that he is simply too ignorant to explain these “in the same style as the rest, namely, by demonstrating effects from causes, and showing from what sort of seeds, and in what manner, nature must produce them.”15 Yet eventually he manages to produce something of a treatise on the formation of animals, even if incomplete, as a component of his Description du corps humain, first published posthumously in 1664. In this work, Descartes begins by describing the initial action of the two parental seeds upon each other, how they, as a result of their heat, “serve as a leaven to each other” (an instance of fermentation, discussed already in chapter 2), which ultimately causes some particles “to gather toward some part of the space that contains them; and, expanding there, they press on the others that surround them, which begins to form the heart.”16
In the Description Descartes has remarkably little to say about the subsequent acquisition of particular traits, save for a rather elaborate account of sexual differentiation, according to which every fetus sends forth its sexual organ in the direction of the mother’s navel, so that if the child is facing toward her back, the “penis” will thrust inward and so result in a girl, while if the child is facing forward it will thrust out and yield a boy. This account raises interesting questions. Mechanism renders even sexual dimorphism something of a mystery: if there is no longer a matter/form dichotomy onto which the male/female one may be mapped, then why is there not simply universal parthenogenesis instead of distinctly sexual reproduction?17
Beyond the problem of sexual differentiation, Descartes also attempts an account of more specific traits. Thus, for example, he adopts the common view that facial hair is a result of “dryness” in the body and explains that “the dryness of males results from the transpiration of spirits through the testes.”18 But what about even more specific traits, not, say, the presence or absence of facial hair, but that hair’s color and texture? What about the exact pigment of the skin, the modality of the earlobes, attached or unattached, or the color of the eyes? Here, Descartes’ account of the development of fetuses is at its most inadequate. There is, it would seem, only a hint of a solution, and it is to be found in scattered comments, later more fully developed by other mechanist philosophers, concerning the formative power of the mother’s imagination.
In a letter of January 29, 1640, Descartes writes to Lazare Meyssonnier (whom he has accused of being misled by astrology, chiromancy, and other stupidities in a letter of the same day to Marin Mersenne)19 that he is suspicious of the fable according to which the urine of a man who has been bitten by a rabid dog contains “effigies of little dogs.” But, he continues, if it actually does happen, this phenomenon should be no less difficult to explain than the causes of “those marks that children receive as a result of the desires [envies] of their mothers.”20 A few months later, he writes to Mersenne, who had worried that such marks might be damaging to Descartes’ account of mind-body interaction, that there is nothing at all so strange about marques d’envie, and he now maintains that there is nothing impossible about the claim concerning the effects of a rabid dog bite.21
In his published works, Descartes makes two references to the marques d’envie that interest Mersenne. One is in La dioptrique: “I could even demonstrate to you, moreover, how sometimes [the image] can pass from [the pineal gland] through the arteries of a pregnant woman into certain parts of the child that she carries in her womb, and how it forms its markings there, which cause such astonishment among the learned.”22 And again in L’homme, in almost exactly these words: “I could add something here about how the traces of [the mother’s] ideas pass through the arteries to the heart, and thus radiate throughout the blood; and about how they can sometimes even be caused by certain actions of the mother to be imprinted on the limbs of the child being formed in the womb.”23
Malebranche, for his part, will make a very significant addition to the history of the mechanist appropriation of the imagination theory: he maintains that without it there would be no possibility of accounting for species reproduction within a mechanist framework. Thus he writes in the Search after Truth of 1676:
It is true that this communication between the brain of the mother and that of her child sometimes has bad results when the mother allows herself to be overwhelmed by some violent passion. Nevertheless, it seems to me that without this communication, women and animals could not easily bring forth young of the same species. For although one can give some explanation of the formation of the fetus in general, as Descartes has tried successfully enough, nevertheless it is very difficult, without this communication of the mother’s brain with the child’s to explain why a mare does not give birth to a calf, or a chicken lay an egg containing a partridge or some bird of a new species.24
Malebranche begins his discussion of the subject with the usual sensationalist anecdotes about defects; his chosen example is of a child born with bones broken in exactly the same places where a publicly executed criminal—whose execution the pregnant woman had the misfortune to witness—had had his own bones broken. He also tells us that women with excessive cravings give birth not only “to deformed infants but also fruits they have wanted to eat, such as apples, pears, grapes, and other similar things.”25 These things happen, he explains, because
infants in their mothers’ womb, whose bodies are not yet fully formed and who are, by themselves, in the most extreme state of weakness and need that can be conceived, must also be united with their mother in the closest imaginable way. And although their soul be separated from their mother’s, their body is not at all detached from hers, and we should therefore conclude that they have the same sensations and passions.26
The “flow of spirits,” Malebranche explains, “excited by the image of the desired fruit, expanding rapidly in a tiny body, is capable of changing its shape because of its softness.”27 The infants become like the things for which their mother has communicated to them a desire. But the mother, since her body is not soft enough to take on the figure of the things she imagines, remains unchanged.
Malebranche, as we have seen, like Leibniz, supports a preformationist version of animal generation, though for Malebranche all future animals are contained not in the spermatozoa of their male ancestors but in the ova (still a strictly hypothetical entity in the seventeenth century) of their female ancestors. All human beings were contained in ovo in our first mother, Eve, and are passed down matrilineally, so to speak, egg contained within egg, until the egg is given its chance to enter what Leibniz would call “the larger theater” by developing into a fetus after being stimulated along this path by the father’s contribution. In Malebranche, then, the great challenge becomes just the opposite of the one faced by Aristotle: how to account, not for resemblance to the mother’s side, but rather for the acquisition of paternal traits. But Malebranche has at least some means of accounting for resemblance to the father, or to paternal relatives known to the mother, that Aristotle lacked: paternal resemblance results from the mother’s having an idea of the father.
Malebranche’s conviction that the formative power of the maternal imagination is required to form an embryo into a member of the particular species to which its parents belong suggests that, in his view, the preexisting egg is not really, strictly speaking, preformed, since until it begins the period of gestation it lacks even a minimal amount of “form,” in the old sense of the word: it lacks that in virtue of which it might be said to belong to one species rather than another. Andrew Pyle, observing this problem in Malebranche, asks, “Can there be organisms that don’t belong to any species?”28 As Pyle rightly notes, Malebranche does seem to retract his claim, cited above, that without the imagination theory we could not account for the production by members of a species of members of the same species. Malebranche writes:
I do not deny that God could have disposed all things necessary for the propagation of the species throughout infinite ages in a manner so precise and regular that mothers would never abort, but would always give birth to children of the same size and colour or, in a word, so similar that they would be taken for one another, without this communication of which we have just spoken.29
On this account, then, the preexisting seed does not have to become a member of a species. It always already is one; indeed, it is an exact copy of all other unborn members of its species, and, it becomes differentiated from them through specific traits, if not generic traits, through the influence of the maternal imagination. The imagination, that is, is responsible for a goat’s becoming speckled, but not for a preexisting seed’s becoming a goat. There is, however, no obvious reason to prefer this statement to the statement that immediately precedes it in the Search after Truth, that we have just cited above, in which Malebranche explicitly affirms that it would be impossible to explain how animals give birth to other animals of the same species without recourse to the imagination theory.
Scholars have generally supposed that the imagination was at most thought to break into the process of fetal development on rare occasions and disrupt the otherwise strictly mechanical process. Yet there is much textual evidence that the maternal imagination does not disrupt a normal process but is itself part of this process; as Descartes says, the mother is the “formative agent of all of the exterior members [formatrix omnium membrorum exteriorum],” regularly communicating images to the fetus through the umbilical arteries that serve to shape and imprint its visible body. This, however, is not, at least from the point of view of a mechanist like Descartes, the intervention in an otherwise physical process of the mental. For images, too, are physical things on his account.
In sum, the role of the maternal imagination in fetal development was adaptable across different ontologies and did not necessarily imply commitment to nonnatural or immaterial forces. And in this respect the maternal imagination provides a useful illustration of a general rule that should guide our interpretation of the nature of seventeenth-century scientific parsimony: while it is true that many natural philosophers sought to pare down the list of forces at work in nature, there is no a priori way for the historian to tell which phenomena were associated with which forces. In other words, a thinker such as Descartes could have a radically minimalist ontology of forces but still remain committed to phenomena that others might explain in terms of the forces he rejects, and that would themselves subsequently be abandoned in the history of science.
Leibniz, for his part, will be intent on arguing that soul activity can have no role in the formation or the maintenance of the body. The fact that he would so much as consider adopting the doctrine of maternal influence in his own writings, as in the passages cited above, is particularly interesting, in view of his frequent insistence that the soul in no way may be seen as having the responsibility for “making the body.” As he writes in his polemic against G. E. Stahl, speaking of Ralph Cudworth and others,
they were mistaken who believed that there would be in the soul, building its own body (or in I-know-not-what other factory supervisor), such a wisdom and power that it could contrive and produce the divine machine of the animal. For the outcome of the artifice is owed to divine preformation.”29
In a sense, the imagination theory transfers the role of the “supervisor” from the developing fetus to the mother on whom it depends for its development. But what need might Leibniz in particular have of this theory? Does it simply enter his work as a result of passive incorporation of ideas that are, as it were, in the air? One possible and very unexpected point of entry into his thought may be a doctrine ordinarily associated with his logic. In 1686, Leibniz presents his well-known “doctrine of marks and traces” in the Discourse on Metaphysics:
There are from all time in the soul of Alexander traces of everything that has happened to him and marks of everything that will happen to him and even traces of all that happens in the universe, though only God can know them all.31
Now one certainly would not want to say that here Leibniz consciously or unconsciously intends to connect the doctrine of marks and traces with embryological considerations. Yet the extent to which his description of concept containment parallels his own accounts elsewhere—as well as the accounts of others, of the way in which fetuses come to acquire traits—is worth noting. Thirteen years earlier, in the Search, Malebranche would claim both that the human fetus inherits from the mother physical traits as a result of her “violent passions” and that similar violent passions of the first parents have left physical traces on the brains of all subsequent generations. He writes that sin is communicated from one generation to the next as a result of “very profound traces from the impression of sensible objects” in our first parents, “which they may well then have communicated to their children.”32 Elsewhere in the same work, Malebranche writes that “many children carry on their faces marks or traces of the idea that struck their mother.”33 It is evident that for Malebranche the “biological” question of the inheritance of traits on the one hand, and on the other the moral and theological problem of the transmission of original sin, are of a pair.
Such an association was indeed widespread in the seventeenth century. As recent ground-breaking work by Richard T. W. Arthur discusses, according to the primarily Lutheran doctrine of traducianism, which Leibniz is known to have held in his youth, original sin is transmitted to children directly from the souls of the parents, and so on back to Adam.34 Thus Leibniz writes to Lambert van Velthuysen in a letter of May 1671, mostly promoting his recently composed Hypothesis physica nova:
I explain by means of this body, in which a mind is implanted, that mind can multiply itself, without new creation, per traducem. . . . Nor do I think traduction is despised by certain theologians except insofar as it seems to imply corporeality and divisibility, and thus mortality. That it does not is shown with as much clarity as sunshine by the very nature of indivisibles. Once this is supposed, it is at least more rational to concede human propagation to be natural than needlessly to invoke God to perform the perpetual miracle of new creation.35
In Daniel Sennert, whose theory of subordinate forms, as we have seen in previous chapters, bears important similarities to Leibniz’s model of nested individuality, traduction is identified explicitly as a notion borrowed from botany, namely, from the grafting of plants:
For example, in trees, in which the seminal force is diffused throughout the whole body, if some part is cut off, and that of some other tree is inserted, the soul of the tree from which the shoot was cut is communicated into the other tree: in the same way, when the soul is conveyed with the semen of animals into the female uterus, so finally from this semen endowed with its own soul the complete animal emerges.36
For Sennert, the theological question of the origins of souls and the “biological” question of the origins of bodies receive one and the same answer. In the context of Leibniz’s philosophy, if we recall that the soul and the body are for him, as it were, two automata running along parallel tracks, then we may perhaps see traducianism as an earlier anticipation, in accounting for the origins of souls, of the parallel account of the origins of bodies that he would later offer by way of the theory of preformation.37
Malebranche’s Search was published while Leibniz was still in Paris, and from the year of its publication Leibniz grappled with Malebranche’s ideas concerning occasionalism and preformation.38 We may assume that prior to its appearance in the Discourse, Leibniz was already familiar with the doctrine of marks and traces in the literal, physical sense in which Malebranche intends it. Catherine Wilson has pointed out that it is often thought that Leibniz’s doctrine of concept containment originated in Leibniz’s logic, in his belief that a proposition is true in virtue of the containment of the predicate in the subject. However, she points out, we need to distinguish sharply between the concept containment theory of truth and the doctrine of marks and traces. While the former remains ontologically neutral as to the subject of the proposition, since, for example, Caesar’s future actions can be contained in the notion of Caesar no matter what kind of thing Caesar is, the doctrine of marks and traces requires that Caesar “must be a substance of a certain type.”39 Namely, Caesar must be the sort of substance on which marks and traces might appear for inspection by an infinitely perceptive eye. The concept containment theory of truth and the doctrine of marks and traces are in many respects analogous to each other, and they are both about substances. But the former is a logical doctrine concerning concepts, while the latter is a doctrine literally about potentially visible properties of the primordia of things. We might be tempted to understand this parallelism as flowing directly from the doctrine of mind-body concomitance, understood as a subdoctrine of preestablished harmony: because every state of a simple substance is always accompanied by a bodily state through which it is explicated, it follows that every predicate contained within the complete concept of an individual substance must have some bodily mark corresponding to it. To be clear, this is not to say that Leibniz thinks of the doctrine of marks and traces as an embryological doctrine, but only that it follows from his commitment (i) to the constant organic embodiment of every substance; and (ii) to the bodily expression of everything contained within that substance’s complete concept, that he is also committed to the view that every developing fetus will have external marks that report, so to speak, the various states of its soul.
As already suggested, what likely prevents Leibniz from adopting the explicitly embryological doctrine of the influence of the maternal imagination that had so occupied Descartes and Malebranche is his commitment to preestablished harmony, and so to the denial of any influence of any sort of external forces upon the body of a developing fetus. For Leibniz, even if we were to think of marks and traces in an embryological sense, as the bodily expression in the embryo of states of the embryo’s soul, still the marks and traces could not be a record of the history of influences upon the body by external forces. Leibniz’s particular doctrine, according to which the marks are always already there in the preformed individual, rather than being seared in at some point in the course of development, obviates the need to give an account of the role of imagination in fetal development.
In the polemic against Stahl of 1709–10, the Halle physician draws heavily on the theory of maternal imagination as support for his own anti-Leibnizian commitment to the real influence of the soul upon the body. Here Leibniz does avow that “it often happens that excessively violent passions of the soul excite great bodily motions, and that the affects of pregnant women manifest themselves in a very remarkable fashion in the formation of the fetus.” Yet he maintains that ultimately this excitation can be cashed out in metaphysical rigor in such a way as to avoid any mention of real mind-body causation. In reality, Leibniz continues, “the soul does not change the laws of the motions and formations of the body,” yet since there is “a correspondence and agreement” between the mother’s soul and the womb, in the case of the formation of the fetus, “we rightly assign this change to the soul, when the state is evident in it from which the corporeal mutation follows.”40 In other words, Leibniz retains the theory of the influence of the maternal imagination, as a sort of “as if” doctrine, even though he recognizes that in metaphysical rigor it violates his causal theory.
Leibniz’s cashing out of the doctrine here, it is interesting to note, is remarkably similar to other attempts to gloss causation41 in a way that saves the traditional manner of talking about the interaction of substances even while denying its possibility at a deeper metaphysical level. In the end, the traits that emerge from the “violent passion” of the mother were already enfolded in the fetus, and before that in the spermatozoon, from the beginning of time. The traits unfold harmoniously with the successive states of the mother, but if one had looked hard enough before this unfolding occurred, one would have found distinct bodily “marks.” The fetus is an automaton, which is to say that every state of it can follow only from its prior states. Another way of putting this is to say that every state of it arises spontaneously or from within.
Such a conception of spontaneity will prove to be important for our understanding of a number of other domains of Leibniz’s natural philosophy as well. Let us turn, in the following section, to the problem of spontaneous generation before moving on in the subsequent section to the question of the origins of fossils.
The influence of the maternal imagination on the developing fetus is one traditional way in which form has often been thought to be imposed on matter through the activity of some sort of mindlike principle. Another is the variety of generation we call “spontaneous.” Indeed, any comprehensive account of the history of spontaneous generation would need to contend with the fact that for most of the history of this theory generation is not “spontaneous” at all, in the sense of “coming out of nowhere,” but rather involves the imposition of form in matter as a result of influx from the intelligent celestial bodies. Such generation may nonetheless count as “spontaneous” in that the forms produced are not produced in any law-like or regular way: there is no regular connection between the form of a barnacle or frog on the one hand and the form of the celestial bodies on the other. On the standard account of spontaneous generation going back to Aristotle, what sort of creature one ends up with is simply a result of the relative proportions of heat and moisture. Nonetheless, in spontaneous generation so understood, as in sexual generation, there is a sort of parent contributing the matter and another contributing the form, and the principle difference is simply that the progenitors are not biological beings, but rather celestial intelligences and terrestrial matter.
Like Ficino before him, the Cambridge Platonist Henry More explicitly describes “spontaneous” generation as resulting from a sort of celestial influx, while also identifying the influence of the mother’s imagination on the developing fetus as simply another instance of the same widespread generative power in nature. In The Immortality of the Soul of 1659, More maintains that the sun and the stars are the “most Intellectual Beings in the world,” and that these have
filled the whole Earth with vital Motion, raising innumerable sorts of Flowers, Herbs and Trees out of the ground. These have also generated the several Kinds of living Creatures. These have filled the Seas with Fishes, the Fields with Beasts, and the Aire with Fowles; the Terrestrial matter being as easily formed into the living shapes of these several Animals by the powerful impress of the Imagination of the Sun and Stars, as the Embryo in the womb is marked by the strong fancy of his Mother that bears him.42
In the same work More argues for a sympathy between earthly and astral bodies as a consequence of their mutual subjection to the “Spirit of Nature.” The universal spirit, More maintains, “is ready to change his own Activity and the yielding Matter into any mode and shape indifferently as the occasion engages him, and so to prepare an edifice, at least the more rude strokes and delineaments thereof, for any Specifick Soul whatsoever, and in any place where the Matter will yield to his operations.”43
This sort of account of spontaneous generation—as imposition of a form from without, whose particular mode and shape remains free of the like-begets-like principle that governs sexual generation—seems to meet its demise at roughly the same time that the theory of sexual generation is transformed, from one of imposition of form by a paternal agent, into either a purely thermomechanical process (Descartes) or the triggering of some primordium (both ovist and animalculist preformation theory). In other words, the generation of frogs from cosmic rays falls out of favor not as a direct result of experimental refutations of spontaneous generation, such as Francesco Redi’s famous 1668 study on maggots, but because the rays had been thought to play a role too analogous to the formal, active principle once attributed to semen but increasingly seen as superfluous. At this point, spontaneous generation comes to be accounted for in terms of heterogenesis, that is, as purely a consequence of putrefaction. According to the theory of heterogenesis, new organisms are not developed out of previously formless matter, but are rather merely the by-products of the decay—that is, the loss of functional unity once explained by the inherence of a form—of dead organisms. As is clear from the previous chapter, before Leibniz had developed his doctrine of preformation, and likely before he could have learned of Redi’s experiments, he had already come to understand “spontaneous” generation as heterogenesis. This is perfectly compatible with preformation, since the worms that arise out of a decaying body are just newly independent corporeal substances that had previously been subordinated to the greater individual within which they were nested.
There were many important factors in the rise of heterogenetic accounts of nonsexual generation. One of these was skeptical libertinism, which relished the possibility that biological kinds, including human beings, have earthly, rather than divine, origins, and that the multifarious life forms we see around us are but the result of chance. In the sixteenth century, Girolamo Cardano and Julius Caesar Scaliger both entertained the possibility that the corpses of large animals could produce new, “perfect” animals or animals that traditionally had been thought to come into being only through the cycle of like begetting like. The libertines even suggested that human beings could arise from such a process.
According to the historian Giuliano Gliozzi, in his monumental study of early modern theories of racial difference, many of the defenders of human spontaneous generation in the sixteenth century were Paduans, and it is reasonable to assume that in that environment they were heavily immersed in Aristotelian biology. Among the more prominent and controversial of these was Lucilio Vanini, whom Gliozzi sees as “connecting the polygeneticism expressed in sixteenth-century naturalism with the version that would take on new forms in the milieux of French libertinism in the first half of the seventeenth.”44 Since there is no upper limit to how much putrescent matter could collect in a bog or mud bank, Vanini argued that the upper boundary for the size, if not the nobility, of a spontaneously generated organism was set largely by environmental circumstances (just as had been the case for Aristotle), in particular, by the extent of the concentration of putrescent matter on the one hand, and the heat of the sun causing it to transform into new life-forms on the other. Repeating a prejudice that goes back at least to Herodotus, Vanini presumed that the environmental circumstances ideal for the spontaneous generation of large animals, as well as of new animal kinds, were most likely to arise in Africa (ex Africa semper aliquid novi, ran the oft-repeated motto).
Vanini is not the only libertine to discern the connection between spontaneous generation and natural origins for humanity. Some, such as François de La Mothe Le Vayer, believed that it is only by appeal to spontaneous generation that we can explain the variety of human-oid, yet evidently soulless, creatures thought to dwell at the edges of the known world. As he writes, “nature is capable of producing on her own—without man’s falling into execrable bestiality—animals that resemble us to such an extent that they force us to say that sometimes there is a greater difference from one man to another than between us and them.”45 La Mothe Le Vayer claims that this is not so hard to conceive if we are willing to draw on the authority of many ancient and medieval authorities, among them Plato,46 Aristotle, Epicurus, Lucretius, and Avicenna, who all acknowledged that “the Earth had [earlier] produced us from herself as [she does] the animals.”47 La Mothe Le Vayer does not simply repeat the heterogenetic theory of the sixteenth-century naturalists; instead, he offers a developmental account according to which “men did not come into being originally in the perfect state in which we see them.”48
The fact that in the Christian tradition, as opposed to the Aristotelian, the first man is born from the earth is worth some reflection. On the face of it, this should not count as an instance of spontaneous generation, since after all Adam is supernaturally created by a God who has a clear idea of what he is creating. In other words, Adam’s creation admits of teleological explanation. With respect to later medieval, Renaissance, and early modern ideas about earthborn creatures, the distinction between these creatures’ mode of generation and that of Adam is not so clear, since they, too, are seen as being generated as a consequence of heavenly or astral influx into terrestrial matter. Of course, the Christian God is meant to be “heavenly” only in a figurative sense, yet God’s role in the first generation of human and animal species bears a remarkable resemblance to medieval and early modern ideas about the celestial “fertilization” of terrestrial matter. The standard nineteenth- and twentieth-century triumphalist accounts of spontaneous generation generally leave out the role of the sun and other heavenly bodies, yet these are almost always invoked by those seeking to define this mode of generation, even critically, in the era in which it was still an option.
In the De generatione animalium, Aristotle mentions, without much explanation, that the pneuma in animal semen is “analogous” to the material of the stars.49 As one commentator notes, while Aristotle did not mean by this that the pneuma originated from the ether, we do find this view springing up in the later Aristotelian tradition.50 Avicenna describes the pneuma as a “virtus informativa” not just analogous to but in fact of the same kind as the virtue of the heavenly bodies.51 Throughout Scholastic philosophy, there is a common presumption that the formative power at work in nature in general is but a different manifestation of the formative faculty traditionally held to govern biological growth and development. This formative power filters down from the celestial to the terrestrial sphere, and in this respect we may say that in all cases of natural growth and development, including the emergence of fossils and crystals as well as of “spontaneously” generated organisms, there is an agent whose role is analogous to the father’s in sexual generation, namely, the heavens.
But, again, this picture of spontaneous generation begins to change with sixteenth-century naturalism and then more radically with the double effect of seventeenth-century mechanism and libertinism. Cartesian embryology, like libertine theories of spontaneous generation, consists in the denial that generation takes place in a broader cosmological context. It is the result of minor causes: an animal fetus for Descartes is nothing ontologically over and above the clots of blood that serve to constitute it, just as a Nile-born ox is for Vanini nothing over and above the sludge from which it emerges.
Where, now, does Leibniz stand with respect to the ontological implications of the various accounts of spontaneous generation?
Leibniz had a clear if transitory early interest in the possibility of a role for the stars in biological growth and development. It is mostly in the very early Directiones of 1671 that we see him considering the possibility of such a phenomenon. He would, however, eventually reject even the possibility of such a role while continuing to believe in the reality of the influence of the imagination on fetal development: a phenomenon that, as we have just seen, was held by many thinkers, including Ficino and More, to be one manifestation of the very same force through which the celestial bodies were held to influence biological processes. Rather than adopting a theory of astral influx to account for spontaneous generation, the young Leibniz would gravitate toward a sort of heterogenesis, according to which new creatures arise not from the imposition of form by the stars on suitably disposed matter but rather through the corruption of older forms and the emergence of newer ones out of these.52
Leibniz’s early model for such an understanding of the generation of insects and worms is evidently the Jesuit scientist Athanasius Kircher.53 “Every living thing,” Kircher writes in his Scrutinium physico-medicum contagiosae luis, quae pestis dicitur (Physico-Medical Investigation of the Contagious Pestilence, Which Is Called Plague) of 1658,
produces from its own decay some congruous animal and different from all others. This we have proved by actual experiment for species of different herbs, and it is true for grain quickened into winged worms. It is just as certain among animals whether highly organized or simple. A dead and rotting ox is quickened into bees. . . . Horses living and dead produce wasps and beetles which for food then suck the blood of the animals that gave them life, to their great annoyance. Human beings (as well as some brutes) generate bedbugs, lice and fleas, which are thus as intimate companions provided by nature to draw off corrupted blood. A dead body, foul with decay, becomes a nursery for worms. Remains of insects, when they rot, produce animals of a similar nature.54
Elsewhere in the Scrutinium Kircher reveals the experimental basis of his conclusions:
Air, Water, and earth teem with innumerable insects capable of ocular demonstration. Everyone knows that decomposing bodies breed worms, but only since the wonderful discovery of the smicroscope [sic] has it been known that every putrid body swarms with innumerable vermicules, a statement which I should not have believed had I not tested its truth by experiments during many years.55
Although most of Kircher’s theories would fall into disrepute, by the middle of the century heterogenesis would prevail over celestial influx as the preferred account of spontaneous generation.56 Leibniz’s early interest in this account of the generation of insects and worms is thus not exceptional, but if we see it as one of the important elements in the eventual emergence of his theory of nested individuality (treated at length in chapter 4), then we may conclude that Leibniz, unlike many of the other supporters of heterogenesis, would see its important implications for key philosophical notions such as substance and individuality.
In his famous 1669 letter to Jakob Thomasius (which Michel Fichant identifies as the young Leibniz’s “lettre-programme,”57 a veritable manifesto), already cited in chapter 4, Leibniz indicates that microscopy is relevant to his thinking about the natural world and signals that it has revealed a sort of universal heterogenesis, not just of creatures ordinarily seen as biological but of such elements as rust as well. The purpose of Leibniz’s letter, specifically, is to show off the ease with which he is able to reconcile the true teaching of Aristotle with the mechanism of the moderns. He begins with the fairly extreme revisionist claim that form in the original Aristotelian sense of “form” can be understood in terms of figure. With this out of the way, he continues: “It remains for us to come to change.” He acknowledges that the moderns account for all change in terms of local motion and tries to make sense of Aristotle’s four-part analysis of cause—that is, into generation and corruption, increase and decrease, alteration, and change of place—in light of the moderns’ simplified analysis. The outcome of his observations in this matter is that the four-part analysis is worth retaining, at least for conceptual purposes, but that strictly speaking, as he writes, “all changes can be explained by motion.” His choice of examples is telling:
I observe in advance that numerically one and the same change may be the generation of one being and the alteration of another; for example, since we know that putrefaction consists in little worms invisible to the naked eye, any putrid infection is an alteration of man, a generation of worm. Hooke shows similarly in his Micrographia that iron rust is a minute forest which has sprung up; to rust is therefore an alteration of iron but a generation of little bushes.58
Nearly the same observation is made in the Theoria motus concreti two years later, where Leibniz argues that the death of living bodies “is invasion by worms, dependent on an invisible fructification.”59 Leibniz speaks of invasion as though the worms are coming from outside, but he also describes the worms as “fructifying” within the body, that is, growing up aboriginally, as it were, out of the physical matter of the dying body. Here death is only relative: while it forces one corporeal substance to retreat to “the smaller theater,”60 it also simultaneously permits countless other corporeal substances to move to the larger theater, to act directly in accordance with their substantial programs rather than subordinately as nested individuals within the greater corporeal substance’s body.
Having explained in the Thomasius letter why he believes that form is nothing but figure, Leibniz goes on to explain that the other basic problem of Aristotelian metaphysics, generation, is not motion but rather the end of motion:
It is no objection that generation occurs in an instant while motion involves succession, for generation is not motion but the end of motion; the motion is already finished at that instant, for a certain figure is produced or generated at the very last instant of motion, as a circle is produced in the final moment of a revolving motion.61
Leibniz appears to be voicing acceptance here of already widespread views, evident in both Kircher and Hooke, according to which: (i) living creatures are generated from the environment, not ex nihilo, as the theory of spontaneous generation is often taken to hold, but rather from some preexisting material, the alteration of which brings about what we call “generation,” but which can be explained in terms of change of place alone, along perfectly mechanistic lines; (ii) there is no fundamental division between the mineral and the vegetable, or, more generally, between the organic and the inorganic; (iii) animal bodies contain the preexisting material, the alteration of which can bring about the generation of new creatures. Putrid infections do not necessarily come from without but can just as easily come from a change of conditions within the body.
Biological theories of heterogenesis may also be traced in part back to chemical theories of subordinate forms. As we have already seen, Leibniz’s shift to the organic model of the body involves a transition from his early animal-economical view, to a view that might be called “chemical Aristotelian,” which has its roots in medieval alchemy, and which, in Leibniz’s own century, is vigorously defended by Sennert. On this view, each body, in addition to its dominant substantial form, contains numerous, actual subordinate forms rather than just the potentiality to give rise to these forms when corrupted or altered. In this connection, William Newman notes a very interesting feature of medieval chemical theories: for the chemists as for the large majority of natural philosophers prior to the modern period, “worms could be seen as a normal decomposition product of such materials as cheese and flesh. Hence the worms were potentially present (in potentia) in a given sample of cheese or flesh, but they were not, of course, actually present (in actu) in the cheese or flesh before those substances became rotten.”62 As Newman explains, for a natural philosopher such as the sixteenth-century chemist Thomas Erastus—who believed that metals can be resolved into oils, waters, and so on, but nonetheless that this does not require that the metals are composed of these things in actu—the implausibility of the body’s actual composition out of worms served as an analogical argument against the chemical theory of the actual composition of metals out of nonmetallic components. For Erastus, a chemist “who states that the normal decomposition products of metals are always present in actu within the undecomposed metals is making a claim tantamount to the absurd view that cheese and flesh are made of worms.”63
As we have seen, however, for Leibniz the example of the body and the worms would only have served to strengthen the anti-Erastean, chemical view that subordinate forms reside in bodies. The worms in the body are indeed there in actu. In fact, on Leibniz’s model of organic body, the very suggestion of spontaneous generation cannot come up: the appearance of worms in a rotting cadaver is only the appearance in the “larger theater” of what was already there. Leibniz’s theory is thus a sort of heterogenetic account of nonsexual generation, according to which generation is the transformation of rotting biomatter into new creatures. The one tremendous difference is that, for Leibniz, when the worms emerge, this is not strictly speaking any sort of genesis at all. One could thus say that whether some change counts as generation or as alteration is for Leibniz a relative question.
Leibnizian heterogenesis is thus starkly different from classical accounts of spontaneous generation: it is neither spontaneous nor is it generation. It is rather more like libertine accounts than the accounts that would take a broad range of natural phenomena to be the result of the imposition of form by some natural or cosmic formative principle. For Leibniz though, unlike for the libertines, it is not motivated by any sympathy for the scandalous idea that human beings might, like worms, be earthborn. Instead, it is motivated by Leibniz’s firm commitment to the perpetual organic preformation of all corporeal substances and by his model of nested individuality, according to which these organically preformed corporeal substances conspire in the constitution of one another’s organic bodies.
Another natural phenomenon taken by many of Leibniz’s predecessors and contemporaries to involve the imposition of form on matter by some supernatural or cosmic generative principle is the production of fossils. Accounting for these objects was a task Leibniz took very seriously, and here most of all we see just how thoroughgoing was his opposition to natural spontaneity, understood as the arising of a new state of created substances undetermined by their prior states.
The speculative sciences of origins in general, and paleontology in particular, complicate our image of early modern science, for since the nineteenth century it has been widely accepted that the sciences that deal with a nonrepeatable past, insusceptible to experimental confirmation, are epistemologically less well founded than sciences such as mechanical physics that are concerned with what bodies do always and everywhere, or what hypothetical bodies would do under hypothetical circumstances. There has also been a tendency, as we have already emphasized, to place the sciences of life further down on the scientific hierarchy than mathematized physics. As we saw in the introduction, Pierre Duhem understands this priority of the one science over the other as resulting from the fact that physics is a “mature science,” to the extent that it seeks to interpret causal relations in terms of an abstract symbolic system, while anatomy, for example, is only a “causal theory,” to the extent that it seeks to explain bare facts in terms of everyday reasoning. From this perspective, paleontology is doubly degraded, for it is interested in the reconstruction of a buried and unrepeatable past by means of traces of formerly living creatures, back to which one refers by the most ordinary causal reasoning at one’s disposal.
Leibniz’s own paleontology is embedded within a much more fundamental debate in early modern natural philosophy concerning the ontology and origins of natural beings and concerning the faculty of the imagination and its role in the generation of forms, the nature and frequency of miracles, and the epistemological limits of any effort to reconstruct events that have been buried in the distant past. His greatest contribution to the history of geology, what we think of as the Protogaea, is largely the result of C. L. Scheidt’s christening of an unfinished manuscript of Leibniz that he, Scheidt, published in 1749. What Leibniz himself refers to as his “Protogaea” is not the work that today bears that name but rather a one-page text published in the Acta Eruditorum of 1693.64 Leibniz’s original title for the manuscript eventually published by Scheidt was De ortu et antiquissimo statu rerum naturalium in regionibus Brunsvic.-Luneb. Dissertatio (Dissertation on the Origin and the Most Ancient State of the Natural Things in the Braunschweig-Lüneburg Regions).65 This title in turn echoes that of a 1665 work by Hermann Conring, De antiquissimo statu Helmestadii et viciniae coniecturae (Conjectures on the Most Ancient Condition of Helmstedt and Vicinity).66
What came to be known as Leibniz’s Protogaea was written between 1691 and 1693, like the short text published in the Acta Eruditorum. The longer work was supposed to serve as the first part of his history of the Guelf family, the ancient lineage that would give rise to the house of Brunswick, of which Leibniz was the secretary and official historian. Leibniz averred that in order to write this history with adequate depth, it would be necessary, so to speak, to begin at the beginning, which is to say to describe the formation of the earth, the oceans, the continents, and the mountains. He was procrastinating, of course, and in the end he succeeded in not completing the task of writing the more recent history he had been assigned until 1714, at which point his employer, the Elector of Hanover, having just been crowned King George I of England, punished him for his tardiness by leaving him behind in Hanover to finish it. The history of the Guelfs picked up speed at this point, but by now Leibniz was too old, and when he died two years later, he left only fragmentary pieces of it completed.
At first glance, the Protogaea seems best categorized as a contribution to the variety of writing that may be called “cosmography,” of which the most prominent examples in the seventeenth century were the works of Steno,67 Kircher, and Thomas Burnet, and also, notably, the third and fourth parts of Descartes’ Principia philosophiae. Leibniz describes his project as a “natural geography” whose aim is “to describe the diverse kinds of terrain and their stratification in different regions.” He explains that this new science will, if done correctly, serve to corroborate the account of Creation familiar from scripture, though in the end he is careful to leave biblical exegesis alone as an autonomous discipline:
These conjectures concerning the infancy of the globe appear plausible, and contain the seeds of a new science that could be called natural geography. But we do not have the pretention of establishing this science, but rather only of making an initial attempt. And without boasting of the agreement that seems to exist between our opinions and the holy scriptures, we will defer to the judgment of those whose task it is to interpret them. And although the vestiges of the primitive world offer uniform indications to us in the present state of things, we do not doubt but that our descendants will judge still better in these matters than we.68
Yet Leibniz’s goals in this work are at least in part much more concrete than the general description he gives of it as “natural geography” reveals. If there is a grain of truth in Leibniz’s affirmation that his account of the origins of the earth are relevant to his history of the Guelf lineage, this is because the part of the earth to which he devotes the most attention, namely, the Harz Mountains, belongs to the current house of Brunswick, and is in fact, in view of its rich silver deposits, an important source of its operating revenue. At the time of writing what we call the Protogaea, Leibniz had recently spent the better part of five years in that region attempting to construct a hydraulic and wind-driven system for generating sufficient energy to excavate the entirety of his employer’s holdings in the Harz.
What we call the Protogaea represents the confluence of two of Leibniz’s long-standing interests: geogony and mineralogy, the one arising from deep natural-philosophical concerns that Leibniz shares with earlier philosophers such as Descartes, the other flowing from practical concerns, most notably having to do with the economic profit to be derived from a well-informed approach to mineral extraction. As for mineralogy, as early as 1682, four years after his first visit to the Harz Mountains, Leibniz expresses a wish to write a treatise on minerals.69 In that same year, Leibniz also publishes the Denkschrift betr. die allgemeine Verbesserung des Bergbaues im Harz (Memorandum concerning the General Improvement of Mining in the Harz), which is a very detailed and thorough analysis of many aspects of the practice of mining, including scientific, economical, and legal ones.70
In the Protogaea, the practical questions of the sort that had been the principle focus of the Denkschrift intermingle with extremely speculative aims,71 aims that are difficult to understand if we do not grasp the importance of speculative cosmogony as a component of seventeenth-century physics. As, for example, parts III and IV of Descartes’ Principia show, before (and during) the Newtonian revolution—which by mathematizing physics made the objects of its study tractable sub specie aeternitatis—it was important for natural philosophers to give not just an explanation of the causes of the motion of bodies but also of their origins.72 As early as the Hypothesis physica nova of 1671, in fact, Leibniz is interested in accounting for the current state of the world in part by appeal to the conditions of its formation.
Certain observations Leibniz makes in the Protogaea indicate that he is not entirely ignorant of the epistemological problems intrinsic to the project of scientifically explaining events and processes buried in the past. Indeed, these are problems that threaten the scientificity not just of paleontology but also of archaeology, historical linguistics, toponymy, and the historia civilis in which Leibniz was naturally inclined, and professionally obligated, to take an interest. He seems, though, to have believed that the evidence that fossils provide must be considered together with what we would today call chemistry, fluid dynamics, stratigraphy, and so on, in order to arrive at a plausible explanation, at a sort of “consilience of inductions,” to use William Whewell’s expression, concerning the origins of fossils. While speculative, Leibniz’s contribution to earth science is remarkable for the effort he makes to remain grounded in the demonstrable.
It is not surprising that the sciences that treat the past, to the extent that they are speculative and undemonstrable, in the seventeenth century easily incorporated mythological elements and tended to rely, in a greater measure than, say, ballistics or hydrology, on the authority of sacred scripture. Descartes’ Le monde is radical in its complete naturalism in the description it offers of the formation of planets, including our own, without any reference to the biblical account of genesis. But Descartes expresses his prudence in a different way: he describes his “world” as an imaginary one and his geogony as a sort of fable. Leibniz, true to his conciliatory spirit, prefers to argue for the harmony of faith and reason and even to reject empirical data when they appear to conflict with the authority of scripture, as, for example, in his reaction to the theory of adaptation (which will be treated in detail in chapter 7):
There are those who take the liberty to make conjectures, to the point of imagining that in the past, when the ocean covered everything, the animals that today inhabit the earth were aquatic, until the moment when their descendants departed from their first home. But this is not in agreement with the holy scriptures, which it is impious to contradict.72
Some commentators see the account of cosmogony given in the Protogaea as compatible with materialism. George MacDonald Ross believes that Leibniz “implicitly admits the looseness of the connection between his account and that in the Bible” when he writes:
But heat or internal motion comes from fire, or light, that is, a highly rarefied permeating spirit. And thus we arrive at a cause of motion, which is where the Holy Scripture also takes up the beginning of cosmogony. So the earliest stage in the formation of things which can be reached by human knowledge, whether by reasoning or by the teaching and tradition of Holy Scripture, is the separation of light and darkness, that is, of active and passive beings; the second stage is the mutual separation of passive beings, that is, the segregation of liquids from dry things.74
“In short,” MacDonald Ross concludes, “throughout his life Leibniz believed it was possible to give a purely materialistic account of the early development of the universe, with only passing reference to the Bible, and none at all to his monadological metaphysics.”75 But the separateness of the kingdoms of nature and grace on the one hand and the activity of immaterial monads on the other is something quite distinct from materialism. From Leibniz’s perspective, there would simply be no reason to drop down to the monadological level in order to accomplish what he sets out to do in the Protogaea. As for compatibility with scripture, all the evidence suggests, at least in this passage, that Leibniz finds the geogonical account given in Genesis to be very useful for his admittedly more detailed approach to the study of the earth.
That said, it is undeniable that certain data were more difficult than others to accommodate within a scripturally based interpretation. One very important difference between Leibniz’s earliest observations on the formation of geographical features and the account he gives in the text of the early 1690s that we call the Protogaea, may be characterized in terms of the demise of spontaneity. In an important undated manuscript discovered by Claudine Cohen, most likely from the mid-1670s, Leibniz gives a very different account of the origins of fossils than the one that would become familiar from the Protogaea:
I can hardly believe that the bones . . . that are sometimes found in the fields, or that one finds while digging in the earth, are always the remains of true giants. Likewise, I can hardly believe that the stones of Malta [i.e., glossopetrae, or sharks’ teeth], which are commonly called serpent tongues . . . are the teeth of fish and that the shells that are found so far from the sea are certain signs [marques] that the sea once covered these places, that she left these shells when she retreated, and that they were subsequently petrified. If this is so, the earth must be much older than the Bible indicates; but I propose by means of a rational process of reasoning to show that this is not the answer. What I believe is that these shapes of animals and shells are usually nothing more than a game of nature: in other words, that they were created independently and have no relation to animals. For it is a fact that stones grow and take on many odd shapes; for proof of this we have only to look at the stones that the R. P. Kircher accumulated in his Mundus subterraneus.76
Here Leibniz evidently does believe that fossils are a result of nature’s spontaneous capacity to throw forth organic forms. An analysis of the terminology and the content of this text places it very early in his career, likely no later than 1671, by which time, as we saw already in chapter 5, Leibniz had begun to shy away from Kircher’s rather florid claims. If we compare this text to Leibniz’s observations on, for example, the power of the stars in the course of earthly affairs, his lack of cautious skepticism regarding Kircher’s already controversial theory is surprising. In any case, we know that whatever the precise date of this text, it expresses a view Leibniz would not hold for long. By the time of the Protogaea one of Leibniz’s most basic convictions would be that nature, as he puts it, does not play.
According to the account of fossils as games of nature, there is a formative or creative faculty in nature that produces the forms of animals in inorganic substrata; it is a sort of superfluous fertility in nature that projects semblances of animals onto rocks or into sediments, simply because it possesses an overabundance of this formative principle and needs to let off steam, as it were, in discharging it without producing real animals in so doing. On this account, if the “spontaneous” generation of animals happens when nature’s (or the celestial bodies’) formative principle is projected into suitably disposed matter, then fossils, in turn, are generated when the same principle is projected into matter, such as rock, that is not so disposed. The belief that fossils are in some way lusus naturae is thus the product of a conception of the generation of all forms in nature on analogy to the generation of animals. It relies on the view that formative principles or seeds, on analogy to the semen of animals, are distributed throughout nature and that everything in nature develops from these principles. A fish produced in stone, on such a view, would be the result of the form of a fish developing out of a formative principle in the wrong kind of material substratum. The result is the semblance of a fish, but one that had never been initially caused by the presence of a real fish. It would be the misfiring of an endlessly productive nature, thrown up gratuitously as a sort of game.
For Leibniz, as we have seen, the generation of organic bodies can be explained entirely in terms of the unfolding and development of preformed corporeal substances, and this development, as well as any other change in the organic body, can be derived, as Leibniz puts it, from the vegetative structure of the body alone. Thus he cannot, in his mature writings, be in agreement with Kircher on the question of fossils, and indeed he denounces the Jesuit’s account of their origins as a fairy tale. But he also cannot accept Descartes’ (superficially fictional) account, according to which the formation of planetary systems, continents, and ultimately organic bodies as well is only a chance result of the initial conditions of the cosmos in conformity with certain minimal laws of nature. Leibniz would hope to find a sort of golden mean between these, according to which everything happens mechanically in nature, even as everything that happens mechanically evidences the divine wisdom behind the Creation. Thus he hopes to defend what we would today call a theory of “intelligent design,” without for that taking recourse to intelligent or spiritual principles subordinate to God that would be responsible for the emergence of organic structure—whether living or fossilized—in the world. His project in the Protogaea thus overlaps, as Cohen and Wakefield have rightly noted, with that of the Theodicy, written two decades later. There, Leibniz describes God’s justice in creating this best of all possible worlds in the following terms:
Perhaps the crust [of the earth] formed by cooling, which had great cavities beneath it, fell, so that we are now only living upon ruins . . . and several floods and inundations have left sediments, of which we find traces and vestiges, which lead us to see that the ocean was in those places that are now the most distant from it. But these revolutions finally stopped, and the globe took the form that we see. Moses insinuates these great changes in few words: the separation of the light from the shadows indicates the fusion caused by fire; the separation of the moist and the dry tells of the effects of floods. But who does not see that these cataclysms [désordres] served to bring things to where they are at present, that we owe to them our riches and our commodities, and that it is by means of them that the globe has been readied to be cultivated by our tending. These disorders [désordres] have passed over into order.77
Physicotheology, nascent capitalism, the protestant work ethic: all are encrusted in the geological strata of our earth. Leibniz’s stratigraphic account of God’s providence may be seen—in certain respects—as a continuation of certain deep-seated ideas about the implantation of the seeds of emerging forms in terrestrial matter. For many in the seventeenth century, the intelligent principle that governs the emergence of new organic forms is not one that is imposed from above by the stars, but rather one that is imbricated in terrestrial matter in the form of seeds. Thus Kircher explains in his Mundus subterraneus of 1665: “God created everything at once. Everything is found hidden in matter that will be produced in the nature of bodies and of material substances.” Although the divine architect created nothing de novo other than matter and the human soul, nonetheless all forms that emerge after the creation are only “developments” made possible by the formative virtue in the seeds, which has existed since the Creation.
For Kircher, it is by means of such seeds that crystals, animals, and fossils alike can be explained. As for the last of these, Kircher believes that fossils are only “prodigious images” generated wherever nature projects a form without having selected a material substratum well-disposed to facilitate that form’s survival as a living being. To use Leibnizian terminology, a fossil for Kircher is an organic body that never comes together with a corporeal substance, whereas, for Leibniz, every organic body is always the organic body of a corporeal substance. Leibniz’s theory of fossils might be understood as a special application of his general theory of the constant organic embodiment of corporeal substances. That is to say that for Leibniz, wherever there is an infinitely integrated structure, there is a living being, and wherever there is a trace or vestige of such an infinitely integrated structure, one may suppose that there was a living being that made it.
For him, therefore, those who believe that fossils are products of nature’s formative power alone “allow themselves to be seduced by the fairy tales . . . of Kircher and Becher, and other authors as vain as they are credulous, who have written of the wonderful games of nature and of her formative power.”78 Leibniz does acknowledge that there are some productions of nature whose origin cannot be determined with certainty. Thus, as concerns ambergris (which as it happens is a hardened, mucous excretion from certain types of whale), “there is not enough of it to determine whether it arises from the mineral, vegetable, or animal kingdom.”79 But ambergris, unlike fossils, is a mass rather than a structure. And Leibniz believes that only organic beings can give rise to organic structures.
In the Protogaea Leibniz relates several examples of fossils that he himself has seen in the Harz Mountains:
I have seen many marine animals, such as the shark, the herring, the lamprey, and this latter sometimes stuck beneath the herring. Looking at these phenomena, most observers are content to say that they are games of nature, a term that is devoid of meaning, and they present to us these ichthyomorphous stones as an example of the undeniable capriciousness of nature’s genius [rerum genii], hoping by this to solve all the difficulties and to prove that nature, this great fabricator, imitates, as if playing, the teeth and bones of animals, shells, and serpents.80
Leibniz notes that the defenders of this sort of explanation often find not only images of animals but also of the face of Christ, of the Virgin, or—the Protestant variant—the face of Martin Luther. “So they believe,” he writes, “that they have discovered Christ and Moses in the cave at Baumann, Apollo and the muses in veins of agate, the Pope and Luther in the stone at Eisleben.”81 He relates a story of the miners of the Harz Mountains who even found the figure of a little man in silver, “of the length of a finger, wearing a miner’s clothing, and carrying a tray full of metal” (the difference between such a homunculus and Swift’s example of a supposed game of nature with which we began is that the little man in silver, unlike the little man in flesh and blood, has been formed in the wrong sort of matter, a matter that does not permit it to move about and act as a real man). Leibniz shrewdly explains that “Christians and miners” are predisposed to perceive those things that are naturally present to their minds. In such cases, “art comes to the aid of nature,” which is to say that the imagination imposes forms where they are not to be found in the matter itself.
But there is a tremendous difference for Leibniz between the fortuitous products of chance and the remains of the organic bodies of corporeal substances. Leibniz is ready to admit that it is possible that the figures of living beings or of particular human beings “which deviate but little from reality” might be produced, “but never to the point that they could be mistaken for the works of Scopas.”82 Chance can never copy exactly, and thus those who argue that the resemblance of a stone to Christ is no less verisimilar than an ichthyomorphous stone run the risk of appearing foolish after a more thorough examination:
But it is to be feared that such poorly measured blows will fall back upon their author, and that an argument drawn from such a perfect resemblance will only prove the contrary of what it was meant to establish. There is such a relationship between these supposed simulacra and real fish, their fins and scales are reproduced with so much precision, and the great number of these images in one place is so great, that we can only suppose a manifest and constant cause, rather than a game or chance, or I-don’t-know-what generative ideas: the inane words of the philosophers.83
Leibniz never denies the possibility of miracles. But for him they must occur with utmost infrequency if there is to be any sense at all in calling them miraculous. Thus, for example, as we have seen, he criticizes Malebranche’s occasionalism on the grounds that the latter would have God intervening at every moment in every event in the world; but if this were the case, Leibniz thinks, there would be nothing to distinguish transubstantiation or the incarnation of Christ, for example, from the most banal events imaginable, such as my own digestion of a meal of untransubstantiated bread. For this reason, Leibniz is staunchly opposed to popular miracles as well: in the case of a weak resemblance of a stone to Christ or of a piece of silver to a miner, the cause can only be attributed to the observer’s power to impose the form by means of the imagination.
In the case of stronger resemblances, whose verisimilitude is strengthened rather than weakened by closer investigation, the resemblance is due to the fact that it is not an image at all, but rather a vestige, which is to say the real thing, transformed by time. The fossil, thus, is no more a work of artifice than was the natural machine from which it is left over.834It is clear that in the Protogaea Leibniz wishes to explicitly bring his theory of organic preformation and his rejection of plastic natures, developed elsewhere and with other concerns in mind, to bear on the debate as to the nature and origins of fossils. In section XVIII, for example, he repeats in the harshest of terms his denunciation of the theory of plastic natures or forces residing in matter:
I often notice that the more attentive one is in observing nature, the more familiar one becomes with its phenomena, and the more one is disposed, also, to accept our opinion. And the most talented men rightly believe that the vestiges of animals and the debris of various other bodies were submerged, and they do not allow themselves to be easily persuaded that organic bodies without antecedents, without a destination, without a germ, are born, outside of all the laws of nature, as a result of I-don’t-know-what plastic force, in the bosom of lime or of stone: these useless matrices.84
By “matrices,” Leibniz clearly wishes to suggest not just “matrix” but also “uterus,” which was commonly denoted by this term. The point is thus to suggest that the earth, unlike a living (female) animal body, is “useless” for the purpose of gestation. According to Leibniz, the formation of crystals, by contrast with that of animals and plants, can be exhaustively analyzed in terms of “external contiguity,” that is to say in terms of the regular repetition of radial and polygonal shapes. The forms of fish or plants in stone could never be reduced in the same way to geometrical motifs. Thus Leibniz continues:
[In the case of organic forms] it is not at all a matter of certain radial bodies and of regular polygons as we see in crystals, garnet, and other gems and fluors, as well as in various other minerals, no more than the figures shaped by hexagonal snow, by beehives, in vitriol and aluminum, by common salt and nitre . . . it is not at all a matter of all that geometry of inanimate nature, which can be easily understood by the juxtaposition of parts, as in crystallization.86
Leibniz denies that it is necessary to take recourse to any process of “gestation” for minerals. He would hope to assimilate the process of mineralogenesis not to embryogenesis but to the construction of artificial machines: in both cases, the thing comes into being through juxtaposition of parts. The crucial distinction is thus not between the “natural” and the “artificial,” but rather between organic entities on the one hand and, on the other, anything that can be exhaustively understood in terms of the geometrical relations of its parts, including crystals as well as machines. Significantly, for entities of the latter sort, a crucial marker of their ontological distinction from organic beings is that they may at least in principle be produced by art. Living beings, in contrast, could never be generated in an alchemical furnace or by any other technological means. With the exception of living beings, then, nature and art are not categorically different from each other: “Nature, in effect, is nothing other than an ars magna, and we do not always distinguish clearly what is fabricated [factitia] from what is natural.”87
These distinctions might be graphically summarized as follows: Clock Crystal Fetus Fossil
Thus, Leibniz makes an effort to distinguish between the process of formation of minerals and crystals and that of biological entities. One of the essential differences between mineralogenesis and embryogenesis is that the former process can be entirely reproduced by human art in an experimental context. Human beings are capable of creating on a small scale what nature does on an immense one: nature, Leibniz writes, “who has mountains as her alembics, and volcanoes as her furnaces.”88 When it comes to what we think of as biological generation, in contrast, our experiments are useless: the homunculus created in the laboratory is only a part of alchemical legend, not of real experiment. It is in this connection that Leibniz has occasion to strongly deny that minerals “gestate” in the earth. At the same time, he is eager to identify the structure and production of minerals with artificial mechanical processes.
Leibniz sets off gestating things—embryos of biological entities—from both mineral and technological entities. Biological entities are the things that cannot be reproduced in alchemical furnaces, unlike the products of geological processes. Geological and technological processes are, further, related to each other to the extent that both provide, or are capable of providing, a means for understanding the other. The volcano can be adequately simulated in a furnace, for example. Biological processes, in turn, are distinguished from both geological and technological ones in view of the infinite complexity of the entities they produce. These latter are distinguished from geological processes as well by the fact that, in the formation of living entities, as we have seen, the imagination can play a formative role: embryogenesis is the only subdomain of nature in which at least apparently spontaneous changes remain acceptable, while “spontaneous” generation in contrast has been reduced to a sort of heterogenesis that is not really genesis at all. The generation of fossils, in turn, in contrast with that of minerals and of the traits of living beings, in no way involves imitation or the projection of an image. Fossils are, rather, only vestiges or remains of real entities.
The idea that fossils are a result of lusus naturae is in the end a vestige of a conception of the generation of all natural forms on analogy to the generation of animals. It depends upon the hypothesis of formative principles distributed throughout nature, and upon the view that everything in nature develops from these principles. A fish produced in stone, from this point of view, would be the result of an ichthyoid formative principle that happens to trigger the process of formation in a material substratum that is not suitable for the production of a full-fledged fish capable of swimming, breathing through gills, and so on. For Leibniz, as we will see more fully in the next chapter, such a frozen fish, a fish without any sort of fishy activity in it, can be no fish at all, since what makes a substance the sort of substance it is, is precisely its activity. Nature could not produce, in his view, an entirely useless or end-less fish, and so the form of a fish frozen in stone cannot be a direct product of nature but only an indirect vestige of nature’s productivity. Nature, in other words, does not play.
One lesson to derive from the study of Leibniz’s engagement with the areas of natural philosophy treated in this chapter is that we must be careful to distinguish between two very different notions of spontaneity in interpreting Leibniz’s philosophy. One takes spontaneity, in the original Latin sense of “spontaneus,” as equivalent to the Greek automatos, that is, the state of being determined only by one’s intrinsic properties, which is to say, in Leibnizian terms, the absence of extrinsic denominations.89 As is well known, this sort of spontaneity is central to Leibniz’s philosophical project. There is another sense of spontaneity, that of being entirely undetermined by prior conditions, either intrinsic or extrinsic, and of arising from the free activity of some mind or mindlike power, influencing the course of material nature without in turn being governed by its laws. As we have seen in this chapter, this variety of spontaneity was often adduced in the explanation in the early modern period of a variety of instances of the emergence of order in biological nature, and it is a variety of spontaneity that Leibniz categorically eschews. In the case of trait acquisition, Leibniz translates the influence of the maternal imagination into the terms of his system of preestablished harmony; in the case of spontaneous generation, Leibniz provides an alternative account in terms of heterogenesis; and in the case of fossils, Leibniz rejects the explanation of them as games of nature in favor of an account that treats them as vestiges of real organic bodies.
Interestingly, over the course of the eighteenth century, this latter notion of spontaneity will make a complete transit from natural philosophy to aesthetics. Art, Friedrich Schiller writes in the second of his 1794 Letters on the Aesthetic Education of Man, is the “son of liberty,” and it longs to receive its law not from the “indigence of matter” but from the necessary conditions of spirit. For Schiller, at the beginning of a man’s life he is treated by nature no differently from the rest of its creatures. But what makes a man a man, Schiller maintains, is that he possesses the power to return, guided by reason, along the steps that nature has earlier obliged him to take, and “of transforming the work of blind compulsion into a work of free choice, and of elevating physical necessity into moral necessity.”90 The human faculty that makes this transformation possible is nothing other than the Spieltrieb, or “play-drive,” the very tendency that Leibniz had sought to expel from nature. At the heart of German Idealism, then, we find the idea that it is exactly the lusus that distinguishes man ontologically from nature in its rigid determination. One could propose—though this proposal will surely have to be developed elsewhere—that the roots of modern aesthetic theory lead directly back to crucial developments in the early modern philosophy of nature. The circumscription of precisely what nature is capable of in the seventeenth century has its echo a century later in the Idealist account of what man is capable of in his liberty and independence from nature. In one way or another, spontaneity, in the sense not of self-determination but of play, will find its place.