Like most philosophers of his age, he coquetted with those final causes which have been named barren virgins, but which might be more fitly termed the hetairæ of philosophy, so constantly have they led men astray.
—T. H. Huxley (1869)
Francis Bacon failed to attain the preferment he desired under Queen Elizabeth (1558–1603) but aspired to rise higher in the administration of King James (1603–1625). His Advancement of Learning (Bacon 1605/1885) was dedicated to the new king and presented proposals for a reformation of education and scholarship with a shift in focus from book-learning and the classics to practical arts and experimental science. Book II opened with a direct address to James:
It might seem to have more convenience, though it comes often otherwise to pass (excellent king), that those which are fruitful in their generations, and have in themselves the foresight of immortality in their descendants, should likewise be more careful of the good estate of future times, unto which they know they must transmit and commend over their dearest pledges. Queen Elizabeth was a sojourner in the world in respect of her unmarried life, and was a blessing to her own times; and yet so as the impression of her good government, besides her happy memory, is not without some effect which doth survive her. But to your Majesty, whom God hath already blessed with so much royal issue, worthy to continue and represent you for ever, and whose useful and fruitful bed doth yet promise many the like renovations, it is proper and agreeable to be conversant not only in the transitory parts of good government, but in those acts also which are in their nature permanent and perpetual. Amongst the which (if affection do not transport me) there is not any more worthy than the further endowment of the world with sound and fruitful knowledge. (76–77)
Elizabeth was a hard act to follow, but Bacon flattered James by alluding to his greater sexual potency. The theme of fruitless females and fruitful males returned in a plea for funding experimental science:
Another defect I note, wherein I shall need some alchemist to help me, who call upon men to sell their books and to build furnaces, quitting and forsaking Minerva and the Muses as barren virgins, and relying upon Vulcan. . . . There will hardly be any main proficience in the disclosing of nature, except there be some allowance for expenses about experiments; whether they be experiments appertaining to Vulcanus or Dædalus, furnace or engine, or any other kind. And therefore as secretaries and spials of princes and states bring in bills for intelligence, so you must allow the spials and intelligencers of nature to bring in their bills; or else you shall be ill advertised. (80)
Bacon assigned physics and metaphysics to distinct domains of scholarship:
Physic should handle that which supposeth in nature only a being and moving; and metaphysic should handle that which supposeth further in nature a reason, understanding, and platform. . . . The one part which is physic, inquireth and handleth the material and efficient causes; and the other which is metaphysic, handleth the formal and final causes. Physic (taking it according to the derivation, and not according to our idiom for medicine) is situate in a middle term or distance between natural history and metaphysic. For natural history describeth the variety of things; physic the causes, but variable or respective causes; and metaphysic the fixed and constant causes. (114)
The focus of the new learning was to be empirical. Fixed and constant causes were of no practical use. Bacon rejected emphatically a role for final causes in the physical domain:
For the handling of final causes, mixed with the rest in physical inquiries, hath intercepted the severe and diligent inquiry of all real and physical causes, and given men the occasion to stay upon these satisfactory and specious causes, to the great arrest and prejudice of further discovery. . . . They are indeed but remoraes and hindrances to stay and slug the ship from further sailing; and have brought this to pass, that the search of the physical causes have been neglected and passed in silence. (118–119)
Bacon prospered under James, being appointed Solicitor General (1607), Attorney General (1613), Lord Chancellor (1618), Baron Verulam (1618), and Viscount St. Alban (1621). Then, he was found guilty of corruption by a parliamentary committee of his enemies and removed from public office (1621). He devoted his remaining years to scholarship. De dignitate et augmentis scientiarum was published in 1623 as an expanded Latin version of The Advancement of Knowledge. In a new section on the practical doctrine of nature, he compared final causes to fruitless females:
Physica siquidem et inquisitio causarum efficientium et materialium producit mechanicam: at metaphysica et inquisitio formarum producit magiam; nam causarum finalium inquisitio sterilis est, et, tanquam virgo Deo consecrata, nihil parit. (Bacon 1623/1829, 192)
In rough paraphrase: “Physics, the investigation of efficient and material causes, produces mechanics, whereas metaphysics, the investigation of forms, produces magic; but the investigation of final causes, like a virgin consecrated to God, gives birth to nothing.” Final causes were without practical application. The principal referrents of virgo Deo consecrata for Bacon’s contemporaries would have been Catholic nuns, but, by the nineteenth century, Bacon is commonly interpreted as having alluded to the vestal virgins and to have described final causes as “barren virgins.” In my readings, Bacon never refers to final causes as “barren virgins,” an epithet he reserved for Minerva and the Muses, although virgo Deo consecrata nihil parit meant more or less the same thing.
René Descartes’s (1641/2011) Fourth Meditation similarly rejected a place for final causes in physics, in his case, because the mind of God was inscrutable:
Since I already know that my nature is very weak and limited and that the nature of God is immense, incomprehensible and infinite, I also know from this that there are innumerable things of which I do not know the causes. For this reason alone, I think there is no role in physics for that whole class of causes which are usually sought in purposes, because I think I cannot investigate God’s purposes without temerity. (39)
Descartes returned to this theme in his Principles of Philosophy (1647/1983):
And so, finally, concerning natural things, we shall not undertake any reasonings from the end which God or nature set Himself in creating these things, and we shall entirely reject from our Philosophy the search for final causes: because we ought not to presume so much of ourselves as to think that we are confidants of His intentions. (14)
Neither Bacon nor Descartes rejected final causes outright, but both believed they should be kept in their place. And that place was not physical inquiry. The allocation of efficient and final causes to separate domains of inquiry has been a long-lasting compromise to which many would subscribe today. Thus William Whewell opined:
Final causes are to be excluded from physical inquiry; that is, we are not to assume that we know the objects of the Creator’s design, and put this assumed purpose in the place of a physical cause. The physical philosopher . . . [makes] no use of the notion of final causes: and it is precisely because he has thus established theories independently of any assumption of an end, that the end, when after all it returns upon him and cannot be evaded, becomes an irresistible evidence of an intelligent legislator. . . . Bacon’s comparison of final causes to the vestal virgins is one of those poignant sayings, so frequent in his writings, which it is not easy to forget. . . . If he had had occasion to develope his simile, full of latent meaning as his similes so often are, he would probably have said, that to these final causes barrenness was no reproach, seeing they ought to be, not the mothers but the daughters of our natural sciences; and that they were barren, not by imperfection of their nature but in order that they might be kept pure and undefiled, and so fit ministers in the temple of God. (1833, 266)
The seventeenth-century exclusion of formal and final causes from scientific explanation bore abundant fruit in investigations of the nonliving world, but nonphysical causes continued to be used as explanatory principles in the study of living beings: teleological concepts of the physiological (normal) and pathological (abnormal) were central to medicine and physiology; naturalists interpreted the intricate adaptations of plants and animals as evidence of a Creator; embryologists interpreted development as proceeding toward a final form. For theists, the compromise of separate explanatory domains of science and theology allowed bodies to be viewed as mechanisms whose form and function revealed the wisdom and beneficence of a divine legislator.
The structures of living things showed clear evidence of aptness for function, but organisms of different species exhibited structural similarities that were difficult to explain solely in terms of a shared purpose. Skeletons of sperm whales possessed pelvic bones, like other mammals, despite the absence of hind limbs. Ostriches had wings, like other birds, but were unable to fly. Mysterious laws of form appeared to exist independent of final causes. The living world contained individuals that belonged to species that could be grouped into genera that could be grouped into more inclusive categories on the basis of “affinities” revealed in correspondences of form or structure. No two individuals were exactly alike, but the members of a species belonged together as deviations from an ideal form. The “same” generic parts could be recognized in different species albeit with specific differences. Taxonomists attempted to bring order to the abundance of living forms with the search for a “natural” system of classification.
Morphology, a term coined by Goethe, developed in the nineteenth century as a science of form. Comparative anatomists found similarities of inner structure despite superficial differences of outward form and looked for nonmaterial principles of explanation. Georges Cuvier championed “des conditions d’existence, vulgairement nommé des causes finales” (“the conditions of existence, commonly named final causes”) (1817, 6) as determining animal form, but others recognized aspects of form that were inexplicable in terms of function. Étienne Geoffroy Saint-Hilaire propounded a unity of organic composition behind the seductions of form and function. He envisaged a single plan expressed in the diverse forms of all animals (Le Guyader 2004). Their disagreements came to a head in a series of debates before the French Academy of Sciences in 1830. Cuvier was generally interpreted as having bested Geoffroy in these debates.
In Indications of the Creator, William Whewell expressed confidence in the doctrine of final causes:
The assumption of hypothetical final causes in physics may have been, as Bacon asserts it to have been, prejudicial to science; but the assumption of unknown final causes in physiology, has given rise to the science. The two branches of speculation, Physics and Physiology, were equally led, by every new phenomenon, to ask their question, “Why?” But, in the former case, “why” meant “through what cause?” in the latter, “for what end?” And though it may be possible to introduce into physiology the doctrine of efficient causes, such a step can never obliterate the obligations which the science owes to the pervading conception of a purpose contained in all organization. (1845, 21)
In distinctly Kantian terms, Whewell saw final causes as constitutive of understanding in both the organic and inorganic worlds but regulative of reasoning about the organic world:
This Idea of a Final Cause is applicable as a fundamental and regulative idea to our speculations concerning organized creatures only. That there is a purpose in many other parts of creation, we find abundant evidence to believe from the arrangements and laws which prevail around us. But this persuasion is not to be allowed to regulate and direct our reasonings with regard to inorganic matter, of which conception the relation of means and ends forms no essential part. In mere Physics, Final Causes as Bacon has observed, are not to be admitted as a principle of reasoning. But in the organical sciences, the assumption of design and purpose in every part of every whole, that is, the pervading idea of Final Cause, is the basis of sound reasoning and the source of true doctrine. (49)
Richard Owen had at first sided with Cuvier and final causes, but his further studies caused him to reconsider his position (Owen 1868, 787). Although he was not ready to derive all forms from a single transcendent plan, he nevertheless recognized a unity of type in the forelimbs of moles, horses, bats, and whales despite disparate functions (Owen 1849). Structural correspondences, in some ill-defined way, expressed “ideas” that were independent of use and details of form. As a result of these studies he found “the artifice of an archetype vertebrate animal was as essential as that of the archetype plant had been to Goethe in expressing analogous ideas; and as the like reference to an ‘ideal type’ must be to all who undertake to make intelligible the ‘unity in variety’ pervading any group of organisms” (Owen 1868, 788). He expressed the continuing discontent of many morphologists with final causes, using a familiar metaphor (Owen 1849, 40):
A final purpose is indeed readily perceived and admitted in regard to the multiplied points of ossification of the skull of the human foetus, and their relation to safe parturition. But when we find that the same ossific centres are established, and in similar order, in the skull of the embryo kangaroo, which is born when an inch in length, and in that of the callow bird that breaks the brittle egg, we feel the truth of Bacon’s comparisons of “final causes” to the Vestal Virgins, and perceive that they would be barren and unproductive of the fruits we are labouring to attain, and would yield us no clue to the comprehension of that law of conformity of which we are in quest.
By the mid-nineteenth century, the mechanical philosophy had secured the field of the physical sciences but the tangled bank of biology remained contested ground. Charles Darwin’s notes from 1838 contain the following:
The Final Cause of innumerable eggs is explained by Malthus.—[is it anomaly in me to talk of Final causes: consider this!—] consider these barren Virgins. (Barrett et al. 1987, 637)
These cryptic words can be interpreted in many ways. An interpretation I find attractive is that “barren virgins” refers to the innumerable eggs (most will die without issue); the Malthusian struggle for existence explains why eggs are produced in such large numbers; and the parenthetical note is an injunction to consider whether natural selection eliminated final causes from the living world or explained them.
In On the Origin of Species, Darwin wrote:
It is generally acknowledged that all organic beings have been formed on two great laws—Unity of Type, and the Conditions of Existence. By unity of type is meant that fundamental agreement in structure, which we see in organic beings of the same class, and which is quite independent of their habits of life. On my theory, unity of type is explained by unity of descent. The expression of conditions of existence, so often insisted on by the illustrious Cuvier, is fully embraced by the principle of natural selection. . . . The law of the Conditions of Existence is the higher law; as it includes, through the inheritance of former adaptations, that of Unity of Type. (1859, 206)
Thus Darwin explained unity of type by transformation in actual evolutionary time rather than abstract formal space and was able to reconcile similarity of structure with divergence of function.
In one of the first reviews of On the Origin of Species, T. H. Huxley suggested that Darwin had charted a course past the sirens of teleology:
The path he bids us follow professes to be, not a mere airy track, fabricated of ideal cobwebs, but a solid and broad bridge of facts. If it be so, it will carry us safely over many a chasm in our knowledge, and lead us to a region free from the snares of those fascinating but barren Virgins, the Final Causes, against whom a high authority has so justly warned us. (1859, 9)
Huxley had missed the head of the nail. Darwin returned to the relation between past and current utility in On the Various Contrivances by which British and Foreign Orchids Are Fertilised by Insects:
Although an organ may not have been originally formed for some special purpose, if it now serves for this end we are justified in saying that it is specially contrived for it. On the same principle, if a man were to make a machine for some special purpose, but were to use old wheels, springs, and pulleys, only slightly altered, the whole machine, with all its parts, might be said to be specially contrived for that purpose. Thus throughout nature almost every part of each living being has probably served, in a slightly modified condition for diverse purposes, and has acted in the living machinery of many ancient and distinct specific forms. (1862, 348)
Darwin believed that investigation of the usefulness “of each trifling detail of structure is far from a barren search to those who believe in natural selection,” but he added the following important caveat:
I do not here refer to the fundamental framework of the plant, such as the remnants of the fifteen primary organs arranged alternately in the five whorls; for nearly all of those who believe in the modification of organic beings will admit that their presence is due to inheritance from a remote parent-form. (1862, 352)
Huxley continued to grapple with the relation between natural selection and final causes. In a review of Ernst Haeckel’s Natürliche Schöpfungs-Geschichte, he opined:
Perhaps the most remarkable service to the philosophy of Biology rendered by Mr. Darwin is the reconciliation of Teleology and Morphology, and the explanation of the facts of both which his views offer. (1869a, 13)
But this was a reconciliation without enthusiasm. Huxley now recognized two kinds of teleology. The first was
the Teleology which supposes that the eye, such as we see it in man or one of the higher Vertebrata, was made with the precise structure which it exhibits, for the purpose of enabling the animal which possesses it to see. (1869a, 14)
This kind of teleology had “undoubtedly received its death-blow” from the doctrine of evolution. The appearance of purpose could be explained by mechanical processes without recourse to final causes. Morphology had been reconciled with a corpse. The second was a “wider Teleology” that viewed the universe as a vast mechanism with an undisclosed purpose. This wider teleology was untouched by the doctrine of evolution but was a subject on which the scientific investigator must remain agnostic:
If the teleologist assert that this, that, or the other result of the working of any part of the mechanism of the universe is its purpose and final cause, the mechanist can always inquire how he knows that it is more than an unessential incident—the mere ticking of the clock, which he mistakes for its function. And there seems to be no reply to this inquiry, any more than to the further, not irrational, question, why trouble one’s self about matters which are out of reach, when the working of the mechanism itself, which is of infinite practical importance, affords scope for all our energies? (1869a, 14)
Huxley still heeded Bacon’s admonition that final causes were barren virgins irrelevant to practical inquiry.
Asa Gray announced that Darwin had not merely reconciled teleology and morphology but had united them in fertile marriage:
Let us recognise Darwin’s great service to Natural Science in bringing back to it Teleology: so that, instead of Morphology versus Teleology, we shall have Morphology wedded to Teleology. In many, no doubt, Evolutionary Teleology comes in such a questionable shape, as to seem shorn of all its goodness; but they will think better of it in time, when their ideas become adjusted, and they see what an impetus the new doctrines have given to investigation. They are much mistaken who suppose that Darwinism is only of speculative importance and perhaps transient interest. In its working application it has proved to be a new power, eminently practical and fruitful. (1874, 81)
Darwin wrote to Gray in rapid response:
What you say about Teleology pleases me especially, and I do not think anyone else has ever noticed the point. I have always said you were the man to hit the nail on the head. (F. Darwin 1898, 367)
What was “the point” that so gratified Darwin? Most commentators have interpreted this to be Gray’s statement that Darwin had wedded Morphology and Teleology, but this reading has problems not least of which is Huxley’s earlier statement that such a reconciliation was Darwin’s “most remarkable service to the philosophy of Biology” (emphasis added). Perhaps, ‘the point’ was what Gray said about the practice of Biology and the impetus to investigation. Final causes were far from barren virgins. They were powers both practical and fruitful.
In two groups of animal, however much they may at present differ from each other in structure and habits, if they pass through the same or similar embryonic stages, we may feel assured that they have both descended from the same or nearly similar parents, and are therefore in that degree closely related. Thus, community in embryonic structure reveals community of descent.
—Charles Darwin (1859)
In On the Origin of Species, Darwin argued that comparative embryology revealed resemblance among related forms because of common descent and differences because of divergent adaptation. He presented his theory of descent with modification as unifying what had been perceived as the conflicting demands of unity of type and conditions of existence. But Darwin’s marriage of form and function was the unwitting source of an estrangement between the study of embryological development, a goal-directed process, and the study of evolutionary transformation by natural selection, a process without a preordained end.
For Aristotle, telos could refer to an endpoint toward which a thing moved or the utilitarian purpose that motivated an action. Since Aristotle, these senses of final cause, of goal and utility, had often been entangled. In the first half of the nineteenth century, “evolution” was generally used to refer to the process of development whereby a thing of one form (an egg or embryo) gave rise to a thing of another form (an adult). In this context, the end (telos) of the living thing was the achievement of its form (eidos). The use of “evolution” to refer to changes of form within a generation was sometimes extended to changes in form across many generations—the modern sense of the term—often with the associated belief that there was an analogy between the two processes of change and that understanding the former would provide insight into the latter. One might say that the emphasis of many nineteenth-century German morphologists was on the goal-directedness of development whereas the emphasis of British naturalists was on utilitarian function (German Zweck has stronger connotations of “goal” or “target” than English purpose).
From his extensive studies of the late-nineteenth century literature, the historian of science Peter Bowler (1983, 1992) concluded that On the Origin of Species catalyzed a widespread acceptance of evolutionary change among biologists but that Darwin’s mechanism of natural selection was largely dismissed. Theories of evolutionary transformation were modeled instead on orderly, goal-directed processes of development. As one example, in On Orthogenesis and the Impotence of Natural Selection in Species-Formation, Theodor Eimer wrote:
Orthogenesis shows that organisms develop in definite directions without the least regard for utility through purely physiological causes as the result of organic growth. (1898, 2)
Such theories embraced the sense of final cause (directedness) that Darwin rejected but rebuffed the sense of final cause (utility) that Darwin embraced. The “evolutionary synthesis” or “modern synthesis” refers to an ill-defined period in the first half of the twentieth century during which evolution by natural selection was recognized as being compatible with Mendelian genetics. A common claim of those now calling for a reformation of evolutionary theory is that developmental biology was “excluded” from the synthesis of this earlier period. Another interpretation is that most leading embryologists in this period chose not to join because they were skeptical about the relevance of natural selection and Mendelian genetics for understanding processes of development (Hamburger 1980).
Despite Darwin’s attempted naturalization of organic purposes, the charms of evolutionary teleology were spurned by most experimental biologists. This was associated with a major shift toward explanations of living things in terms of physics and chemistry. During the nineteenth century, this shift can be seen first in physiology and then in the emerging fields of biochemistry, cell biology, and experimental embryology. The inorganic and organic worlds were seen as subject to the same fundamental laws. Because final causes had long been rejected by physicists and chemists, they were also rejected by those who wanted to subsume biology under chemistry and physics. The rise of mechanistic biology was well underway in the nineteenth century and became the dominant strain of twentieth-century biology.
As early as 1842, Emil du Bois-Reymond and Ernst Brücke had sworn to uphold the truth that the only forces active within organisms were physicochemical forces (du Bois-Reymond 1918, 108). Hermann Helmholtz and Carl Ludwig joined the oath-takers in a program to reform physiology in purely physicochemical terms (Cranefield 1957). Helmholtz spelled out the consequences of his principle of “conservation of force” for living things:
There may be other agents acting in the living body, than those agents which act in the inorganic world; but those forces, as far as they cause chemical or mechanical influences in the body, must be quite of the same character as inorganic forces, in this at the least, that their effects must be ruled by necessity, and must be always the same, when acting in the same conditions, and that there cannot exist any arbitrary choice in the direction of their actions. (1861, 357)
For most mechanists, the conservation of force negated the possibility that organisms could be unmoved movers, capable of arbitrary choices without prior physical cause.
The “mechanistic revolution” has been far more important than the “Darwinian revolution” in shaping the experimental practices and scientific philosophies of most modern biologists. Darwinism has not been central to their work. Some welcomed the justification that the evolutionary hypothesis provided for fundamental similarities in the inner workings of diverse organisms because it justified medically relevant research in yeast. Others saw Darwinism as a vindication of materialism and a justification for the elimination of final causes from nature. Many found the metaphor of natural selection to be scientifically suspect, especially its intentional overtones.
By the mid-twentieth century, mechanism had stormed the ramparts of biology and cleared the field for material and efficient causes. There were always some biologists who championed nonphysical causes, but they increasingly presented themselves as heretics against the rigid orthodoxy of hegemonic mechanism. During my own education, I was repeatedly warned against teleological thinking, and its close cousin anthropomorphism, by lecturers who spoke of the heart as a pump for the circulation of blood and of RNAs as messengers for the translation of proteins. The seventeenth-century rejection of a role for final causes in scientific inquiry has had long-lasting effects on the ideology of working scientists. Concepts of purpose and function shape the practice of biology—this is the natural way to think about living things—but the overt language of teleology is censored. Final causes are shunned as fruitless females who remain anathema to the virile vulcans of hard science.