In Berlin, in daily contact with La Mettrie, notorious atheist and author of Man a Machine, and with the growing atheism of the king himself, his former “pupil,” Voltaire reviews his thoughts in a dialogue. He pits the materialist doctrines of Lucretius, a first century BCE Roman poet and philosopher, against his contemporary Posidonius, not well known in the eighteenth century, but who, as a Stoic, might feasibly adopt a deistic view. The growing adamancy of atheists was becoming a new concern,1 and a topic Voltaire would return to repeatedly, for he felt, sometimes using the Roman Empire as an example, that atheism could be fatal to virtue, except among real philosophers—and especially among kings, or persons wielding great power.2
FIRST DISCUSSION
POSIDONIUS
Your poetry is sometimes admirable, but Epicurean physics seem very wrong to me.
LUCRETIUS
What! You don't want to admit that atoms arranged themselves in a way that produced the universe?
POSIDONIUS
We mathematicians can only admit things that are evidently proven by incontestable principles.
LUCRETIUS
My principles are
Ex nihilo nihil, in nihilum nil posse reverti;
Tangere enim et tangi nisi corpus nulla potest res.
From nothing comes nothing, nothing returns to nothing;
And one body is only touched by another body.
POSIDONIUS
Even if I accord you these principles, and even atoms and empty space, you will no more persuade me that the universe formed itself in the admirable order that we see than if you told the Romans that Posidonius’ armillary sphere made itself.
LUCRETIUS
But who then made the world?
POSIDONIUS
An intelligent being, more superior to the world and to me than I am to the copper I composed my sphere with.
LUCRETIUS
You who only admit evident things, how can you recognize a principle of which you have no notion?
POSIDONIUS
Just as, before meeting you, I judged that your book was written by an intelligent man.
LUCRETIUS
You admit that matter is eternal, that it exists because it exists. Therefore, if it exists by its nature, why can it not form suns, planets, plants, animals and men by its nature?
POSIDONIUS
All the philosophers who came before us thought matter eternal, but they did not prove it. And if it were eternal, this does not prove that it could form objects in which such sublime design is so apparent. This rock can be as eternal as you like, you will not convince me that it can produce Homer's Iliad.
LUCRETIUS
No, a rock will not produce the Iliad, any more than it will a horse. But matter, organized over time and become a mix of bone and flesh and blood will produce a horse, and, organized more finely, will compose the Iliad.
POSIDONIUS
You suppose it with no proof, and I must admit nothing without proof. I will give you bones and blood and flesh already made. I'll let you and all the Epicureans in the world work on it. Would you agree to make a deal in which you will possess the Roman Empire if you manage to make a horse with these prepared ingredients, or be hanged if you can't?
LUCRETIUS
No. That surpasses my powers, but not those of nature. It takes millions of centuries for nature, after having passed through all possible forms, to arrive at the only one which can make living beings.
POSIDONIUS
You can shake all the materials of the earth in a barrel your entire life, you will not so much as pull one well-shaped object from it; you will make nothing. If the time of your entire life cannot produce so much as a mushroom, will the lifetime of another man suffice? Why could several centuries do what one century cannot? You would have to have seen humans and animals born from earth, or wheat without seeds, etc., etc., to dare confirm that matter alone can take on such forms. No one that I know has ever seen such a thing. Therefore, no one should believe it.
LUCRETIUS
All right then! Humans, animals, trees have always existed. All the philosophers agree that matter is eternal. They will agree that generations are as well. It is in the nature of matter that celestial bodies turn, that birds fly, that horses run and that men make Iliads.
POSIDONIUS
In this new assumption, you change your opinion, but you still suppose what is in question. You admit a thing of which you have not the slightest proof.
LUCRETIUS
I am allowed to think that what exists today existed yesterday, existed a century ago, a hundred centuries ago, and going back interminably. I am using your argument. No one saw the sun and other heavenly bodies begin their course, the first animals get formed and come to life. We may therefore think that everything has been as it is eternally.
POSIDONIUS
There is a big difference. I see an admirable design, and I am forced to think that an intelligent being formed this design.
LUCRETIUS
You should not admit a being you have no knowledge of.
POSIDONIUS
That is like telling me that I should not admit an architect built the Capitoline because I was unable to see this architect.
LUCRETIUS
Your comparison is not valid. You have seen houses built and you have seen architects. Therefore you should think that a man much like the architects today built the Capitoline. But things are different in this instance. The Capitoline does not exist by its nature, and matter does. It is impossible for matter not to have a given form. So why do you not want it to possess by its nature the form it has today? Is it not far easier to imagine nature modifying herself than to imagine an invisible being modifying it? In the first case, you have only one difficulty, which is to understand how nature acts. In the second, you have two, which are to understand this same nature and an unknown being that acts upon her.
POSIDONIUS
It's just the contrary. I not only see the difficulty, but the impossibility of understanding that matter can have infinite designs, and I see no difficulty in accepting an intelligent being who governs this matter through infinite designs and through an all-powerful will.
LUCRETIUS
What! It is because your mind cannot understand one thing that it presumes something else? So it is because you cannot seize the art and mainsprings necessary for nature to arrange itself in planets, the sun, and animals that you resort to another being?
POSIDONIUS
No. I do not resort to a God because I cannot understand nature, but I understand that nature manifestly needs a supreme intelligence, and that is the sole reason that would prove God to me, if I did not have other proofs on top of it.
LUCRETIUS
And if this matter had intelligence on its own?
POSIDONIUS
To me it is obvious that it does not.
LUCRETIUS
And to me it is obvious that it does, since I see bodies like you and me who reason.
POSIDONIUS
If matter possessed reason in and of itself, you would have to say that it possesses it necessarily. However if this attribute were necessary to it, it would have it at all times and in all places, because a necessary attribute can never be separate from it. A piece of mud, the most vile excrement would think. Yet you will surely not say that dung thinks. Thought is therefore not a necessary attribute of matter.
LUCRETIUS
Your reasoning is a sophism. I hold movement to be necessary to matter. Nevertheless, this pile of dung, this heap of mud, are not presently in movement. They will be, when pushed by some body. By the same token, thought will only be an attribute of this body when this body will be organized to think.
POSIDONIUS
Your error comes from the fact that you always suppose what is in question. You do not see that to organize a body, to make it a man, a thinking being, thought needs to exist already; it needs a design that has been decided. Yet you cannot admit designs before the sole beings who have designs here below have been formed. You cannot admit of thoughts before the beings which have thoughts exist. You suppose what is in question again when you say that movement is necessary to matter, since what is absolutely necessary exists always; like extent exists in every form of matter. Movement however does not always exist. The pyramids of Egypt are certainly not in movement. Even if some subtle matter passed between the stones of the pyramids of Egypt, the mass of the pyramid is immobile. Movement is therefore not absolutely necessary to matter. It comes from somewhere else, just as thought comes to human beings from elsewhere. There is therefore an intelligent, powerful being that gives movement, life, and thought.
LUCRETIUS
I can answer that by saying that there has always been movement and intelligence in the world. This movement and intelligence have been distributed throughout all time, following the laws of nature. Matter being eternal, it is impossible that it didn't exist in some kind of order. It could not be in any order without movement and thought. Intelligence and movement were therefore necessarily in it.
POSIDONIUS
Whichever way you look at it, you can only make suppositions. You suppose an order. Therefore some intelligence was needed to arrange this order. You suppose movement and thought before matter was in movement and before there were human beings and thoughts. You cannot deny that thought is not essential to matter, since you dare not say that a stone thinks. You can only oppose perhapses to the truth pressing in on you. You sense the powerlessness of matter, and you are forced to admit a supreme being, intelligent, all-powerful, who organized matter and thinking beings. The design of this superior intelligence bursts forth on all sides, and you must perceive it in a blade of grass as in the course of the stars. We see that everything is directed toward a certain end.
LUCRETIUS
Are you not taking for a design what is only a necessary existence? Are you not taking for a certain end what is only the use we make of things that exist? The Argonauts built a ship to go to Colchis. Will you say that trees were created for the Argonauts to build a ship and that the sea was made so that the Argonauts could undertake their journey? Men wear shoes. Will you say that legs were made by a Supreme Being to be shoed? No, undoubtedly. But the Argonauts, having seen wood, built a ship, and having known that water could carry this ship, they undertook their voyage. Likewise, after an infinity of forms and combinations that matter adopted, it happened that the humors and the transparent cornea that compose an eye, formerly separated in different parts of the human body, became united in the head, and animals began to see. The organs of generation, which were scattered, assembled and took the form they have. Then generations were produced with regularity. The matter of the sun, long spread out throughout space, conglobed and made the star that lights us. Is anything impossible in all that?
POSIDONIUS
In truth you cannot seriously resort to such a system. First of all, in adopting this hypothesis, you abandon the eternal generations you spoke of earlier. Secondly, you are mistaken regarding final causes. There are voluntary uses we make of the gifts of nature; and there are indispensable effects. The Argonauts might not have used trees of the forests to make a ship, but these trees were visibly destined to grow on earth and to produce fruit and leaves. We can perfectly well not shoe our legs, but the leg was visibly made to carry the body and to walk, eyes to see, ears to hear, reproductive organs to perpetuate the species. If you consider that from a star, placed four or five hundred million leagues away from us, come rays of light that make the same determined angle in the eyes of every animal, and all those animals instantaneously have the same sensation of light, you will admit to me that there is a mechanism, an admirable design there. Therefore is it not unreasonable to admit a mechanism without an artisan, a design without intelligence, and such designs without a Supreme Being?
LUCRETIUS
If I admit this Supreme Being, what form will he have? Is he in a place? Is he beyond all space? Is he in time, or outside of time? Does he fill all space, or not? Why would he have made this world? What is his goal? Why create sensitive and unhappy beings? Why does moral and physical pain exist? Whichever way I look, I see only the incomprehensible.
POSIDONIUS
It is precisely because this Supreme Being exists that his nature must be incomprehensible, because if he exists, there must be infinity between him and us. We must admit that he exists, without knowing what he is, and how he operates. Are you not forced to admit asymptotes in geometry, without understanding how these lines can approach each other eternally yet never meet? Are there not things just as incomprehensible yet demonstrated in the properties of a circle? Conceive the fact then that we must admit the incomprehensible when the existence of this incomprehensible thing is proven.
LUCRETIUS
What! I would have to renounce the dogmas of Epicurus?
POSIDONIUS
Better to renounce Epicurus than reason.
SECOND DISCUSSION
LUCRETIUS
I'm beginning to recognize a Supreme Being inaccessible to our senses and proven by our reason, who made the world and preserves it, but as to everything I said about the soul in my third book, admired by all the learned of Rome, I don't think you can oblige me to renounce it.
POSIDONIUS
You say first:
Idque situm media regione in pectoris hoeret.
The spirit is in the middle of the chest.
But when you composed your lovely verses, did you not make any effort with your head? When you spoke of the intelligence of Cicero or of the orator Mark Antony, did you not say he had a good head? And if you had said he had a good chest, would people not think you were speaking of his voice or his lungs?
LUCRETIUS
But do you not feel that it is around the heart that feelings of joy, of pain, and of fear are formed?
Hic exultat enim pavor ac metus; haec loca circum Laetitiae mulcent.3
Do you not feel your heart expand or tighten at good or bad news? Are there not secret springs there that relax or take on elasticity? It is hence there the seat of the soul.
POSIDONIUS
There is a set of nerves that starts at the brain, passes by the stomach and the heart and descends into the reproductive parts, and which registers movements upon them. Will you say that human understanding resides in the reproductive parts?
LUCRETIUS
No, I wouldn't dare say that. But even if I place the soul in the head, instead of in the chest, my principles will remain: the soul will still be an infinitely loosened matter, similar to the elementary fire that animates the whole machine.
POSIDONIUS
And how do you conceive that a loosened matter can have thoughts and feelings by itself?
LUCRETIUS
Because I experience it, because every part of my body being touched feels it. Because this feeling is spread throughout my whole machine, because it cannot be spread there except by an extremely subtle, rapid matter. Because I am a body, because a body can only be agitated by another body, because the interior of my body can only be penetrated by very loose corpuscles, and because my soul can consequently only be an assemblage of these corpuscles.
POSIDONIUS
We already agreed in our first discussion that it doesn't appear that a rock could compose the Iliad. Would a sunray be more capable of it? Imagine this sunray a hundred thousand times more subtle and rapid. This clarity, this subtleness, would it form sentiments and thoughts?
LUCRETIUS
Perhaps it would if it were in organs prepared for it.
POSIDONIUS
There you go with your perhapses again. Fire can no more think for itself than ice can. If I were to suppose that it is fire that thinks in you, that feels, that has a will, you would then be forced to admit that it isn't by itself that fire has a will, feelings, and thoughts.
LUCRETIUS
No, it wouldn't be by itself, it would be by the joining of this fire and my organs.
POSIDONIUS
How can you imagine that two things that do not think when on their own produce thought when they are united?
LUCRETIUS
Much like a tree and soil, taken separately, do not bear fruit, and bear it when the tree has been put in the soil.
POSIDONIUS
The comparison only dazzles. This tree carries the seed of its fruit; you can see it in its buds. And the sap of the soil develops the substance of these fruits. Fire would therefore need to carry the germ of thought, and the body's organs would have to develop this seed.
LUCRETIUS
What do you see impossible about it?
POSIDONIUS
I find that fire, this quintessential matter, does not possess the right to thought any more than a rock does. Something produced should contain something similar to what produces it. Yet a thought, a desire, a feeling, have nothing in common to igneous matter.
LUCRETIUS
Two objects that collide produce movement, and yet movement has nothing in common with these two objects. It does not have three dimensions as they do. It has no shape. So a thing can have nothing similar to the thing which produces it. Therefore a thought can be born of the joining of two things that have no thought.
POSIDONIUS
This comparison is again more dazzling than accurate. I see only matter in two objects in movement. I only see objects moving from one place to another. But when we reason together, I can see no matter in your ideas nor in mine. I will tell you only that I no more conceive of how one object has the power to move another than I can conceive of how I have ideas. They are both things equally inexplicable to me, and both prove to me equally the existence and power of a Supreme Being, author of both movement and thought.
LUCRETIUS
If our soul is not a subtle fire, an ethereal quintessence, what then is it?
POSIDONIUS
You and I have no idea. I will gladly tell you what it is not, but I cannot tell you what it is. I see that it is a power that is within me, that I did not give myself this power, and that consequently it comes from a being superior to me.
LUCRETIUS
You did not give yourself life. You received it from your father. You received thought with life from him, just as he received it from his father, and so on, going back to infinity. You no more know at heart what the principle of life is than you know what the principle of thought is. This succession of living, thinking beings has existed from all time.
POSIDONIUS
I still see that you are forced to abandon the system of Epicurus, and that you no longer dare say that the declension of atoms produces thought. But I have already refuted the eternal succession of feeling, thinking beings at our last discussion. I told you that if material thinking beings existed on their own, thought would have to be a necessary attribute to all matter; that if matter thought necessarily by itself, all matter would have thought. But that is not the case. Therefore a succession of material beings thinking on their own is untenable.
LUCRETIUS
This reasoning you repeat does not prevent a father from passing a soul on to his son while forming his body. This soul and body grow together. They fortify each other, are subject to illness and to the infirmities of old age. Our judgment deteriorates with the decline of our physical strength. The effect finally ceases with the cause, and the soul dissolves like smoke in air.
Praeterea, gigni partier cum corpore, et una
Crescere entimus, pariterque senescere mentem.
Nam velut infirmo pueri teneroque vagantur
Corpore; sic animi sequitur sententia tenuis
Inde, ubi robustis adolevit viribus aetas,
Consilium quoque majus, et auctior est animis vis:
Post, ubi jam validis quassatum est viribus aevi
Corpus, et obtusis ceciderunt viribus artus,
Claudicat ingenium, delirat linguaque mensque;
Omnia deficiunt, atque uno tempore desunt.
Ergo dissolvi quoque convenit omnem animai
Naturam, ceu tumus in altas aeris auras:
Quandoquidem gigni pariter, pariterque videtur
Crescere; et, ut docui, simul aevo fessa fatiscit.
(Bk. III, v. 446)4
POSIDONIUS
Those are some fine verses, but do you teach me the nature of the soul with them?
LUCRETIUS
No, I relate its story to you, and I reason with a bit of verisimilitude.
POSIDONIUS
Where is the likelihood that a father transmits the faculty of thinking to his son?
LUCRETIUS
Do you not see every day that children have the inclinations of their fathers, just as they have their features?
POSIDONIUS
But does a father creating his son not act as a blind instrument? Did he intend to make a soul, to make thoughts, in climaxing with his wife? Do either one know how a child is formed in the womb? Must we not resort to some superior cause in all the other operations of nature we have examined? Do you not sense, if you are of good faith, that men give nothing to themselves and that they are all in the hands of an absolute master?
LUCRETIUS
If you know more than I do, tell me what a soul is then.
POSIDONIUS
I don't pretend to know more than you. Let us enlighten each other. Tell me first what vegetation is.
LUCRETIUS
It is an internal movement that carries the sustenance of the earth into a plant, makes it grow, develops its fruit, extends its leaves, etc.
POSIDONIUS
You don't think, undoubtedly, that there is a being called vegetation that works these marvels?
LUCRETIUS
Whoever did?
POSIDONIUS
You must conclude from our preceding discussion that the tree did not give itself vegetation.
LUCRETIUS
I am forced to agree.
POSIDONIUS
And life? You can tell me what it is?
LUCRETIUS
It's vegetation with feeling in an organized body.
POSIDONIUS
And there is not a being called life that gave this feeling to an organized body.
LUCRETIUS
Without a doubt. Vegetation and life are words that refer to things that vegetate and live.
POSIDONIUS
If the tree and animals cannot give themselves vegetation and life, can you give yourself thoughts?
LUCRETIUS
I think that I can, for I think what I want. My will was to speak to you of metaphysics, and I'm speaking of them to you.
POSIDONIUS
Do you think you are the master of your thoughts? You know then what thoughts you will have in an hour, or in a quarter of an hour?
LUCRETIUS
I confess that I have no idea.
POSIDONIUS
You often have ideas while sleeping. You compose verses in your dreams. Caesar takes towns. I resolve problems. Hunting dogs chase deer in their dreams. Ideas then come to us independently of our will. So they are given to us by a superior force.
LUCRETIUS
How do you imagine it? Do you claim that a Supreme Being is continually occupied with giving ideas, or that he creates incorporeal substances that then have ideas on their own, sometimes with the help of the senses, sometimes without? Do these substances form at the moment of the animal's conception? Are they formed beforehand, and do they wait for bodies to slip into? Or do they lodge in them only when the animal is ready to receive them? Or is it in the Supreme Being that every animated being sees the idea of things? What do you think?
POSIDONIUS
When you tell me how our will effects a movement in our bodies instantly, how your arm obeys your will, how we receive life, how our foods are digested, how wheat turns into blood, I will tell you how we get ideas. I confess my ignorance on all that. The world may shed new lights one day, but from Thales up to our day, we haven't any. All we can do is feel our powerlessness, recognize an all-powerful being, and beware of systems.