The Principles of Aristotle's Philosophy

Wherein it is shown that he never observed the second part of the general rule, and wherein his four elements and elementary qualities are examined.

In order that one may make some comparison between the philosophy of Descartes and that of Aristotle, it is proper that I represent in abstract what the latter thought of elements and natural bodies in general, and what the most learned believe he did in his four books On the Heavens; for his eight books of Physics belong rather to logic or, if you will, to metaphysics than to physics, since they consist of nothing but vague and general words that represent no distinct and particular idea to the mind. These four books are entitled On the Heavens because the sky is the principal of the simple bodies of which he treats.

This philosopher begins this work by proving that the world is perfect, and here is his proof:

All bodies have three dimensions; they cannot have more, for the number three comprises everything, according to the Pythagoreans. Now, the world is the assemblage of all bodies: therefore the world is perfect.

One could, by this amusing proof, also demonstrate that the world cannot be more imperfect than it is, since it cannot be composed of parts that have fewer than three dimensions.

Critique of Aristotle’s Axioms on Motion

In the second chapter, he first supposes certain Peripatetic truths:

1. All natural bodies have within themselves the power to move themselves

This he proves neither here nor elsewhere.

On the contrary, he asserts in Chapter 1 of Book 2 of Physics that it is ridiculous to attempt to prove it because:

• it is self-evident
• only those who cannot discern what is known by itself from what is not, pause to prove what is evident by what is obscure.

But it has been shown elsewhere that:

• it is absolutely false that natural bodies have within themselves the power to move themselves
• this appears evident only to those who, like Aristotle, follow the impressions of their senses and make no use of their reason.

2. All local motion occurs in a straight or circular line, or one composed of the straight and the circular

But, if he did not wish to think about what he so rashly advances, he ought at least to have opened his eyes, and he would have seen that there are motions in an infinity of different ways that are not composed of the straight and the circular; or rather, he ought to have thought that motions composed of straight-line motions can occur in an infinity of ways, if one supposes that the component motions increase or decrease their speed in an infinity of different ways, as can be seen by what was said previously.

There are, he says, only these two simple motions, the straight and the circular: therefore all motions are composed of those two. But he is mistaken: circular motion is not simple; one cannot conceive it without thinking of a point to which the moving body—or rather the motion—relates, and everything that encloses a relation is relative and not simple.

But if one defines simple motion, as one ought, as that which always tends toward the same place, circular motion would be infinitely composite, since all the tangents of the circular line tend toward different places. One can define the circle in relation to the center; but to judge the simplicity of circular motion in relation to a point with respect to which there is no motion would be a very poor way to go about it.

3. All simple motions are of 3 kinds:

• one from the center
• another toward the center
• around the center

But it is false that the last one is simple. It is also false that there are no simple motions except those that go from bottom to top and from top to bottom; for all motions in a straight line are simple, whether they approach or recede from the center, or whether they approach or recede from the poles or any other point. Every body, he says, is composed of 3 dimensions: therefore the motion of all bodies must have three simple motions. What a relationship between simple motions and dimensions! Furthermore, every body has three dimensions, and no body has a motion composed of these three simple motions.

4. He supposes that bodies are either simple or composite.

He says that simple bodies are those that have within themselves some power that moves them, like fire, earth, etc., and that composite bodies receive their motion from those that compose them.

But, in this sense, there are no simple bodies, for there are none that have within themselves any principle of their motion; there are also no composite bodies, since composites suppose the simples which do not exist. Thus, there would be no bodies at all. What an imagination, to define the simplicity of bodies by a power to move themselves!

What distinct ideas can one attach to these words “simple bodies” and “composite bodies” if simple bodies are defined only in relation to an imaginary force of motion?

The Nature of the Heavens and the “Evil Genius” of Aristotelian Logic

What are the consequences he draws from these principles:

Circular motion is a simple motion. The heavens move circularly. Therefore their motion is simple. Simple motion can only belong to a simple body – to a body that moves by its own forces. Therefore, the heavens are a simple body, distinct from the four elements, which move along straight lines.

This entire reasoning contains only false and absurd propositions.

Let us examine his other proofs, for he brings forward many wretched ones to prove a thing as useless as it is false.

His second reason for proving that the heavens are a simple body distinct from the four elements supposes that there are two kinds of motions: one natural, and the other contrary to nature or violent.

But it is clear enough to all those who judge things by clear ideas that, since bodies have no nature or principle of their motion themselves (as Aristotle understands it), there is no violent motion or motion contrary to nature. It is indifferent to all bodies to be moved or not to be moved: to be moved in one direction or to be moved in another.

But Aristotle, who judges things by the impressions of the senses, imagines that bodies which, by the laws of the communication of motion, always place themselves in such a situation with respect to others, do so by themselves because they are better off there and because it is more conformable to their nature.

Here, then, is Aristotle’s reasoning:

The circular motion of the heavens is either natural or contrary to nature.

He says that:

• if it is natural to them, the heavens are a simple body distinct from the elements, since the elements do not move circularly by their natural motion.
• If the circular motion is contrary to the nature of the heavens, then the heavens must be one of the elements, like fire, or something else.

The heavens cannot be any of the elements; for instance, if the heavens were made of fire, the natural motion of fire being from bottom to top, the heavens would have two contrary motions, the circular and that from bottom to top; which cannot be, since a body cannot have two contrary motions. If the heavens are some other body that does not move circularly by its nature, it will have some other natural motion, which cannot be. For if it moves by its nature from bottom to top, it will be fire or air; if from top to bottom, it will be water or earth: therefore, etc.

I do not pause to point out in detail the absurdities of these reasonings; I say only in general that what Aristotle says here signifies nothing distinct, and that there is nothing true or even conclusive in it.

His third reason is this:

The first and most perfect of all simple motions must be the motion of a simple body, and even of the first and most perfect of simple bodies. But circular motion is the first and most perfect of simple motions, because every circular line is perfect and there is no straight line that is so. For if it is finite, something can be added to it; if infinite, it is still not perfect, since it has no end, and things are perfect only when they are finished. Therefore, circular motion is the first and most perfect of motions. Therefore, the body that moves circularly is simple, and the first and most divine of simple bodies.

Here is his fourth reason:

All motion is natural or it is not, and any motion that is not natural to some bodies is natural to some others. We see that motions from top to bottom and from bottom to top, which are not natural to one body, are natural to others, for fire does not naturally descend, but earth naturally descends. Now, circular motion is not natural to the four elements; there must therefore be a simple body to which this motion is natural. Therefore, the heavens, which move circularly, are a simple body distinct from the four elements.

Finally, circular motion is either natural or violent to some body. If it is natural, it is evident that this body must be among the simple and most perfect. If it is not natural, it is very strange that this motion lasts forever, since we see that all motions that are not natural last only a very short time. One must therefore believe, after all these reasons, that there is some other body separate from all those that surround us, which is of a nature all the more perfect as it is more distant from us.

This is how Aristotle reasons. But I defy the most intelligent of his interpreters to attach distinct ideas to the terms he uses, and to show that this philosopher begins with the simplest things before speaking of the most composite, which is absolutely necessary for reasoning justly, as I have just proved.

Chapter-by-Chapter Errors in Book 1 of On the Heavens

Aristotle’s manner of philosophizing is entirely useless for discovering the truth.

He himself says in Chapter 5 that those who mistake at first in something are 10,000 times more mistaken if they advance far, it being visible that he does not know what he says in the first two chapters of his book, one must believe that it is not safe to yield to his authority without examining his reasons.

But so that one may be even more persuaded of this, I will show that there is no chapter in this first Book where there is not some impertinence.

• In Chapter 3 he says that the heavens are incorruptible and incapable of any alteration; he brings forward several rather playful proofs for this, such as that it is the dwelling place of the immortal gods, and that no change has ever been noticed there. The last of these proofs would be good enough if he said that someone had returned from there, or that he had been close enough to the celestial bodies to notice their changes. But I do not know if today anyone would yield to his authority, because telescopes teach us the contrary.

• In Chapter 4, he pretends to prove that circular motion has no contrary. Nevertheless, it is manifest that motion from east to west is contrary to that which occurs from west to east.

• In the fifth chapter, he poorly proves that bodies are not infinite, because he draws his proof from the motions of simple bodies. For what prevents there being, above his primum mobile, some further extension that is without motion?
• In the sixth chapter, he amuses himself uselessly by proving that the elements are not infinite. For who can doubt it, when one supposes, as he does, that they are enclosed within the heavens that surround them? But he makes himself ridiculous when he decides to prove it by their weight (pesanteur) and their lightness (légèreté). If the elements were infinite, he says, there would be an infinite weight and lightness, which cannot be. Therefore, etc. Those who wish to know his proof more at length may read it in his books; I should think it a waste of time to report it.
• In the seventh chapter, he continues to prove that bodies are not infinite, and his first proof supposes that it is necessary for every body to be in motion, which he does not prove and which cannot be proved.
• In the eighth chapter, he maintains that there are not several worlds of the same kind, for this pleasant reason: that if there were another earth than the one we inhabit, earth being heavy by its nature, that earth would have to fall upon ours, because ours is the center where all heavy bodies must fall. From where did he learn this, if not from his senses?
• In the ninth chapter, he proves that it is not even possible for there to be several worlds, because if there were any body above the heavens, it would be simple or composite, in a natural or violent state, which cannot be, for reasons he draws from the three kinds of motions of which he has already spoken.
• In the tenth chapter, he asserts that the world is eternal, because it cannot be that it began to be and yet lasts forever, since we see that everything that is made corrupts over time. He learned this from his senses. But who taught him that the world will last forever?
• In the eleventh chapter, he employs himself in explaining what is meant by “incorruptible,” as if ambiguity were greatly to be feared and he were to make great use of his explanation. Yet this term “incorruptible” is so clear by itself that Aristotle does not trouble himself to explain either in what sense it must be taken, or in what sense he takes it. It would have been more proper had he defined an infinity of terms he uses, which awaken nothing but sensible ideas, for one might perhaps have learned something by reading his works.
• In the final chapter of this first book, he tries to show that the world is incorruptible because it cannot be that it began and yet lasts eternally. All things, he says, subsist during a finite or infinite time. But what is infinite only in one sense is neither finite nor infinite. Therefore nothing can subsist in this manner.

This is the manner in which reasons the prince of philosophers and the genius of nature, who, instead of making known by clear and distinct ideas the true cause of natural effects, establishes a pagan philosophy upon the false and confused ideas of the senses, or upon ideas too general to be useful in the search for truth.

I do not reproach Aristotle here for not knowing that God created the world in time to make known His power and the dependence of creatures, and that He will never annihilate it so that it may also be known that He is immutable and never repents of His designs. But I believe I can reproach him for proving, by reasons that have no force, that the world is from all eternity. If he is sometimes excusable in the opinions he maintains, he is almost never excusable in the reasons he brings forward when he treats of subjects that contain any difficulty.

On the Four Elements and Elementary Qualities

But in order to be convinced that the “genius of nature” will never discover its secrets or its springs to men, it is proper that I show that the principles upon which this philosopher reasons to explain natural effects have no solidity.

One can discover nothing in physics if one does not begin with the simplest bodies, that is to say, with the elements; for elements are the bodies into which all others resolve, because they are contained in them either actually or potentially—it is thus that Aristotle defines them.

But one will not find in the works of Aristotle that he explained by a distinct idea these simple bodies into which he pretends the others resolve, and consequently, his elements not being clearly known, it is impossible to discover the nature of the bodies composed of them.

This philosopher says indeed that there are four elements—fire, air, water, and earth—but he does not clearly make known their nature; he gives no distinct idea of them; he does not even want his elements to be the fire, air, water, and earth that we see; for after all, if that were so, we should at least have some knowledge of them through our senses.

On several places in his works he tries to explain them by the qualities of heat and cold, moisture and dryness, weight and lightness. But this manner of explaining them is so impertinent and ridiculous that one cannot conceive how so many learned men have content themselves with it. This is what I am going to show.

Aristotle’s Derivation of the Four Elements

Aristotle pretends, in On the Heavens, that:

• the earth is at the center of the world
• all the bodies it pleases him to call simple (because he supposes that they move by their nature) must move by simple motions.

He asserts that besides circular motion—which he maintains is simple and by which he proves that the sky is a simple body—there are only two that are simple: one from top to bottom (or from the circumference toward the center), and the other from bottom to top (or from the center toward the circumference).

He claims these simple motions belong to simple bodies, and consequently that earth and fire are simple bodies, of which one is entirely heavy and the other entirely light.

But because weight and lightness can belong to a body either entirely or in part, he concludes that there are yet two other elements or simple bodies, of which one is light in part and the other heavy in part—namely, water and air. This is how he proves that there are four elements and no more.

All these propositions are false, or at least that they cannot pass for clear and incontestable principles of which one has very clear and distinct ideas.

There is nothing more absurd than wanting to establish the number of elements by imaginary qualities of weight and lightness, saying without any proof that there are bodies which are heavy and others which are light by their nature.

It is therefore ridiculous to suppose, as incontestable principles, that bodies are light or heavy by their nature; on the contrary, it is evident that no body has in itself the power to move itself, and that it is indifferent to it to be moved from top to bottom, or from bottom to top; from east to west, or from west to east.

The Breakdown of the Four Qualities

Let us grant Aristotle his four elements, what consequence can one draw from them for the knowledge of the universe? These four elements are not the fire, air, water, and earth we see. We do not know them by the senses, and still less by reason.

Aristotle declares that there are four principal qualities belonging to the touch: heat, cold, moisture, and dryness, from which all others are composed; and he distributes these primary qualities to the four elements in this manner:

• Fire: Hot and dry
• Air: Hot and moist
• Water: Cold and moist
• Earth: Cold and dry

He asserts that heat and cold are active qualities, and that dryness and moisture are passive qualities. He defines them as follows:

• Heat: That which assembles things of the same kind.
• Cold: That which assembles all things, whether of the same or of different kinds.
• Moisture (The Humid): That which is not easily contained within its own bounds, but within foreign bounds.
• Dryness (The Sec): That which is easily contained within its own bounds and does not easily accommodate itself to the bounds of surrounding bodies.

Critique of the Definition of Heat and Cold

See then what is missing from these principles:

First, Aristotle attaches no distinct idea to the word “quality”: one does not know whether, by quality, he means a real being distinct from matter, or only the modification of matter.

Secondly, the definitions he gives of the first four qualities are all false or useless. Take his definition of heat: Heat is that which assembles things of the same nature. It is false that heat assembles things of the same nature. Heat does not assemble the parts of water; it rather dissipates them into vapor. It does not assemble the parts of wine, nor those of any other liquor or fluid body, nor even those of quicksilver; on the contrary, it dissolves and separates all solid and fluid bodies of the same and of different nature.

In third place, heat in truth can neither assemble nor dissipate the parts of any body; for to assemble or separate the parts of some body, it is necessary to move them: now heat cannot move anything, or at least it is not evident that it can. One sees well that fire moves and separates the parts of bodies exposed to it, it is true, but it is perhaps not by its heat, for it is not even evident that it has any. It is rather by the action of its parts, which are visibly in a continual motion. It is evident that the parts of fire, coming to strike against some body, must communicate to it a part of their motion. If Aristotle had first distinguished the sensation of heat from the motion of the small parts, and had then defined heat as that which agitates and separates the invisible parts of which visible bodies are composed, he would have given a tolerable definition.

Aristotle defines cold as that which assembles bodies of the same or of different nature. This definition is also worthless, for it is false that cold assembles bodies. To assemble them, it must move them; but cold cannot move anything. In fact, by coldness, one means either what one feels when one is cold, or what causes the sensation of coldness: now it is clear that the sensation of coldness cannot move anything. As for what causes the sensation, it is nothing but the rest or cessation of motion. Thus, coldness in bodies being nothing but the cessation of that kind of motion which accompanies heat, it is evident that if heat separates, coldness simply does not separate.

Aristotle, judging things by the senses, imagines that coldness is as positive as heat, because the sensations of heat and cold are both real and positive; and he also thinks that these two qualities are active. It is impossible to discover any certain and incontestable truth by relying only on the senses to judge the qualities of bodies; from several people who touch water that is a little lukewarm, some find it hot, and others cold. Those who are warm find it cold, and those who are cold find it hot. It is the same with the air; it seems hot or cold according to the different dispositions of the body of those who are exposed to it. Aristotle pretends it is hot, but I do not think those who live toward the north are of his opinion…