De principiis naturae

There are, then, three principles of nature: namely, matter, form, and privation. Of these, one — form — is that toward which generation tends, while the other two belong to that from which generation proceeds. Hence matter and privation are the same in subject but differ in account: for the very same thing which is bronze is unshaped before the coming of the form, but it is called bronze in one sense and unshaped in another. Hence privation is said to be a principle not per se but per accidens, since it coincides with matter — just as we say it is accidental that the doctor builds: for he builds not insofar as he is a doctor but insofar as he is a builder, which coincides with being a doctor in one subject. But accident is twofold: namely, the necessary kind, which is not separated from the thing, as risibility in man, and the non-necessary kind, which is separated, as whiteness from man. Hence, although privation is an accidental principle, it does not follow that it is not necessary for generation, since matter is never stripped of privation: for insofar as it is under one form, it has the privation of another, and conversely — as in fire there is privation of air, and in air privation of fire. And it should be known that, since generation is from non-being, we do not say that negation is a principle, but privation: for negation does not determine a subject for itself — 'does not see' can be said even of non-beings, as 'a chimaera does not see', and again of beings not apt by nature to have sight, as stones. But privation is said only of a determinate subject, in which a habit is apt by nature to come about — as blindness is said only of things apt by nature to see. And since generation does not come from non-being simply, but from the non-being which is in some subject — and not in just any, but in a determinate one (for fire does not come from just any non-fire, but from such non-fire as is apt by nature to receive the form of fire) — privation is therefore said to be a principle. But in this it differs from the others, since the others are principles both in being and in becoming: for a statue to come about, bronze must exist, and the figure of the statue must come last; and again, once it is a statue, these two must exist. But privation is a principle in becoming and not in being: for while the statue is becoming, it must not be a statue — if it were, it would not be becoming, since what becomes is not, except in successive things. But once it is a statue, there is no privation of statue in it, since affirmation and negation are not simultaneous, nor likewise privation and habit. Again, privation is an accidental principle, as explained above, while the other two are per se principles. From what has been said, then, it is clear that matter differs from form and from privation in account. For matter is that in which form and privation are understood — as in bronze, figure and the unshaped are understood. Sometimes matter is named together with privation, sometimes without privation: as bronze, being the matter of a statue, does not imply privation, since from saying 'bronze' nothing unarranged or unshaped is understood; but flour, being matter with respect to bread, implies in itself the privation of the form of bread, since from saying 'flour' is signified the unarrangement or disorder opposed to the form of bread. And since in generation the matter or subject remains, while privation does not — nor the composite of matter and privation — the matter which does not imply privation is permanent, while what implies it is transient. But it should be known that some matter has composition of form: as bronze, though it is matter with respect to a statue, is itself composed of matter and form; and therefore bronze is not called prime matter, since it has matter. But matter itself is what is understood apart from any form or privation, but as subject to form and privation, since before it there is no other matter. This is also called yle. And since all definition and all knowledge is through form, prime matter cannot be known or defined of itself, but only by comparison — as when we say that prime matter is what stands to all forms and privations as bronze stands to a statue and to the unshaped. And it is called simply first. Something can also be called prime matter with respect to some genus, as water is the matter of fusible things — though it is not simply first, since it is composed of matter and form, and hence has a prior matter. And it should be known that prime matter, and also form, is neither generated nor corrupted: for all generation is toward something from something, and what generation is from is matter, while what it is toward is form. If matter or form were generated, matter would have matter and form would have form, to infinity. Hence, properly speaking, generation belongs only to the composite. It should also be known that prime matter is said to be one in number in all things. But 'one in number' is said in two ways: as having one form determinate in number, as Socrates — and in this way prime matter is not said to be one in number, since it has no form in itself; and as being without the dispositions that make for difference in number — and in this way prime matter is said to be one in number, since it is understood apart from all the dispositions from which numerical difference arises. And it should be known that although matter has in its nature no form or privation — as in the account of bronze there is neither the shaped nor the unshaped — yet it is never stripped of form and privation: at one time it is under one form, at another under another. But of itself it can never exist, since having no form in its account, it has no actual being — actual being comes only from form — but is only in potency. And therefore whatever is actual cannot be called prime matter.

From what has been said, then, it is clear that there are three principles of nature, namely matter, form, and privation; these are not sufficient for generation. For what is in potency cannot reduce itself to act, just as bronze, which is potentially a statue, does not make itself into a statue, but needs a worker to draw the form of the statue from potency into act. Nor would the form draw itself from potency into act — and I speak of the form of the thing generated, which we said is the terminus of generation; for form exists only in the finished product, while what operates is in becoming, that is, while the thing is coming to be. Therefore besides matter and form there must be some principle that acts, and this is said to be the efficient cause, or mover, or agent, or that from which is the principle of motion. And because, as Aristotle says in II Metaphysics, everything that acts acts only by intending something, there must be a fourth thing, namely what is intended by the worker: and this is called the end. And it should be known that every agent, both natural and voluntary, intends an end, yet it does not follow that every agent knows the end or deliberates about the end. For to know the end is necessary in those whose actions are not determinate but are open to opposites, as voluntary agents are; and therefore they must know the end by which they determine their actions. But in natural agents the actions are determinate: hence it is not necessary to choose the means to the end. And Avicenna gives the example of the lyre-player, who need not deliberate about each plucking of the strings, since the pluckings are determinate in him; otherwise there would be a pause between pluckings, which would be discordant. But deliberation seems more characteristic of one who acts voluntarily than of a natural agent. And so it is clear by an argument from the greater that a natural agent can intend an end without deliberation: and this intending was nothing other than having a natural inclination to something. From what has been said, therefore, it is clear that there are four causes, namely the material, efficient, formal, and final. Although principle and cause are said convertibly, as is said in V Metaphysics, Aristotle nevertheless in the book of the Physics posits four causes and three principles. He takes causes for both extrinsic and intrinsic: matter and form are called intrinsic to the thing because they are parts constituting the thing; the efficient and the final are called extrinsic because they are outside the thing; but by principles he understands only intrinsic causes. Privation, however, is not named among the causes, because it is a principle per accidens, as has been said. And when we say four causes, we understand causes per se, to which however causes per accidens are reduced, because everything that is per accidens is reduced to what is per se.

But although in I Physics Aristotle posits principles for intrinsic causes, nevertheless, as is said in XI Metaphysics, principle is properly said of extrinsic causes, element of the causes that are parts of the thing, that is, of intrinsic causes, and cause is said of both; yet sometimes one is put for the other: for every cause can be called a principle and every principle a cause. Still, cause seems to add something beyond principle commonly so called, because what is first, whether the being of the later follows or not, can be called a principle, as the smith is called the principle of the knife in that the being of the knife comes from his operation; but when something is moved from blackness to whiteness, black is said to be the principle of that motion, and universally everything from which the being of motion begins is called a principle: yet blackness is not that from which the being of whiteness follows. But only that first from which follows the being of the later is called a cause: hence it is said that a cause is that from whose being another follows; and therefore the first from which the being of motion begins cannot be called a per se cause, even if it is called a principle. And for this reason privation is placed among principles and not among causes, because privation is that from which generation begins; but it can also be called a per accidens cause, insofar as it coincides with matter, as explained above.

Element, however, is properly said only of the causes from which there is composition of the thing, which are properly material; and again not of just any material cause, but of that from which the first composition comes, just as limbs are not elements of man, because limbs too are composed of other things: but we say that earth and water are elements, because these are not composed of other bodies, but from them comes the first composition of natural bodies. Hence Aristotle says in V Metaphysics that an element is that from which a thing is first composed, and is in it, and is not divided according to form.

The exposition of the first clause, from which a thing is first composed, is clear from what we have said. The second clause, namely and is in it, is added to distinguish that matter which is wholly corrupted through generation, as bread is the matter of blood, but blood is not generated unless the bread is corrupted, so bread does not remain in the blood: hence bread cannot be called an element of blood; but elements must in some way remain, since they are not corrupted, as is said in the book On Generation. The third clause, namely and is not divided according to form, is added to distinguish those things that have parts diverse in form, that is in species, as a hand whose parts are flesh and bones which differ in species; but an element is not divided into parts diverse in species, as water, every part of which is water. For it is not required for the being of an element that it not be divided according to quantity, but it suffices if it is not divided according to species; and even if it is not divided, it is called an element, as letters are called the elements of words. It is clear, therefore, that principle in a way extends more broadly than cause, and cause than element: and this is what the Commentator says in V Metaphysics.

Having seen, then, that there are four genera of causes, it should be known that it is not impossible for the same thing to have several causes, as a statue whose causes are bronze and the craftsman — but the craftsman as efficient cause, bronze as matter. Nor is it impossible for the same thing to be the cause of contraries, as the helmsman is the cause of the safety of the ship and of its sinking, but of the latter by absence, of the former by presence.

It should also be known that it is possible for one and the same thing to be cause and caused with respect to the same thing, but in different ways: as walking is the cause of health as efficient, while health is the cause of walking as an end, for walking is sometimes for the sake of health; and likewise the body is the matter of the soul, while the soul is the form of the body. For the efficient is called a cause with respect to the end, since the end is not in act except through the operation of the agent; but the end is called the cause of the efficient, since the agent operates only through intending the end. Hence the efficient is the cause of that which is the end — that health may be — yet it does not make the end to be an end; and so it is not the cause of the causality of the end, that is, it does not make the end to be final: as the physician makes health to be in act, yet does not make health to be an end.

The end, however, is not the cause of that which is the efficient, but is the cause that the efficient be efficient; for health does not make the physician to be a physician — and I mean the health that is actually the end of the worker — but it makes the physician to be efficient. Hence the end is the cause of the causality of the efficient, because it makes the efficient to be efficient: and likewise it makes matter to be matter and form to be form, since matter does not receive form except on account of the end, and form does not perfect matter except on account of the end. Hence it is said that the end is the cause of causes, because it is the cause of causality in all causes.

For matter is said to be the cause of form insofar as form exists only in matter; and likewise form is said to be the cause of matter, insofar as matter has being in act only through form: for matter and form are said relatively to each other, as is said in II Physics. For the efficient is the cause of the end insofar as it is ordered to what follows: as parts are to the whole and the simple to the composite.

But because every cause, insofar as it is a cause, is naturally prior to what is caused, it should be known that prior is said in two ways, as Aristotle says in XVI On Animals: through their diversity something can be called prior and posterior with respect to the same thing, both cause and caused. For something is said to be prior to another in generation and time, and again in substance and completeness. Since, therefore, the operation of nature proceeds from the imperfect to the complete, the imperfect is prior to the perfect in generation and time, but the perfect is prior in completeness: as it can be said that the man is before the boy in substance and completeness, but the boy is before the man in generation and time. But although in generable things the imperfect is prior to the perfect and potency prior to act, considering in one and the same thing that first it is imperfect and in potency and then perfect and in act, still speaking simply act and the perfect must be prior, because what reduces potency to act is in act, and what perfects the imperfect is perfect. Matter is indeed prior to form in generation and time, for what a thing comes to is prior to what comes to it; form, however, is prior to matter in perfection, because matter has complete being only through form. Likewise the efficient is prior to the end in generation and time, since motion toward the end comes about from the efficient; but the end is prior to the efficient insofar as it is efficient in substance and completeness, since the action of the efficient is not completed except through the end. Therefore these two causes, namely matter and the efficient, are prior by the way of generation, while form and end are prior by the way of perfection. And it should be noted that necessity is twofold, namely absolute necessity and conditional necessity. Absolute necessity is that which proceeds from the causes prior in the way of generation, which are matter and the efficient, as the necessity of death which comes from matter and from the disposition of the contraries composing [the thing]; and this is called absolute because it has no impediment; this is also called the necessity of matter. Conditional necessity, however, proceeds from the causes posterior in generation, namely from form and end, as when we say that conception must exist if a man is to be generated; and this is conditional, because this woman's conceiving is not necessary simply, but under a condition: if a man is to be generated. And this is called the necessity of the end. And it should be known that three causes can coincide in one, namely form, end, and efficient, as is clear in the generation of fire: for fire generates fire, so fire is the efficient cause insofar as it generates; and again fire is form insofar as it makes to be in act what was previously in potency; and again it is the end insofar as it is the terminus set by the agent and insofar as the operations of the agent are terminated in it.

But the end is twofold, namely the end of generation and the end of the thing generated: as in the generation of a knife: for the form of the knife is the end of the generation, but cutting, which is the operation of the knife, is the end of the knife itself, namely of the thing generated. The end of generation sometimes coincides, from two of the causes mentioned, namely when generation comes about from a like in species, as man generates man and the olive generates the olive; which cannot be understood of the end of the thing generated.

It should be known, however, that the end coincides with the form in the same in number, because the end of generation and the form of the thing generated are the same in number: as the soul is the end and the form of the man generated. But with the efficient it does not coincide in the same in number, but in the same in species; for it is impossible for the maker and the made to be the same in number, but they can be the same in species: as when man generates man, the generating man and the generated man are diverse in number, but the same in species. Matter, however, does not coincide with the end in the same in number nor in the same in species, because matter is imperfect while the end is perfect: but the other causes, since they are in act, have the character of the perfect; and the perfect and the imperfect do not coincide in the same.

Having seen, then, that there are four causes, namely the efficient, material, formal, and final, it should be known that each of these causes is divided in many ways. For one thing is said to be a prior cause and another a posterior cause: as we say that art and the doctor are the cause of health, but art is the prior cause and the doctor the posterior cause; and likewise in the formal cause and in the other causes.

And note that we must always trace the question back to the first cause; as if it is asked "Why is this man healthy?", it is to be answered "Because the doctor healed him"; and again "Why did the doctor heal him?", "On account of the art of healing which he possesses."

It should be known that to say "proximate cause" is the same as to say "posterior cause," and "remote cause" the same as "prior cause"; hence these two divisions of causes, the one into prior and posterior causes and the one into remote and proximate causes, signify the same thing. This, however, is to be observed: that what is more universal is always called the remote cause, and what is more particular the proximate cause: as we say that the proximate form of man is his definition, namely rational mortal animal, but animal is more remote, and again substance still more remote. For all higher things are forms of the lower. And likewise the proximate matter of a statue is copper, but the remote matter is metal, and still more remote, body.

Again, of causes one is per se and another per accidens. A per se cause is said to be the cause of a thing insofar as it is of that kind, as the builder is the cause of the house and wood the matter of the bench. A per accidens cause is that which is incidental to the per se cause, as when we say "The grammarian builds"; for the grammarian is said to be the cause of the building per accidens, for it is not insofar as he is a grammarian but insofar as it is incidental to the builder. And so it is in the other causes.

Again, of causes one is simple and another composite. A cause is called simple when only that which is per se the cause is said to be the cause, or even only that which is per accidens: as if we say that the builder is the cause of the house, and likewise if we say that the doctor is the cause of the house. But it is called composite when both are said to be the cause, as if we say "The doctor-builder is the cause of the house." A cause can also be called simple, as Avicenna explains, in the sense of that which is a cause without the addition of another, as copper is of the statue, for without the addition of any other matter the statue is made from copper; and thus it is said that the doctor produces health, or that fire heats. But a cause is composite when several things must concur for it to be a cause, as one man alone is not the cause of the movement of a ship, but many; and as one stone is not the matter of a house, but many.

Again, of causes one is in act and another in potency. A cause in act is one that actually causes the thing, as the builder when he is building, or copper when the statue is from it; but a cause in potency is one which, although it does not actually cause the thing, can nevertheless cause it, as the builder when he is not building. And it should be known that, speaking of causes in act, the cause and the caused must exist together, so that if one exists, so does the other: for if there is a builder in act, he must be building, and if there is building in act, there must be a builder in act. But this is not necessary in causes that are only in potency.

It should be known, moreover, that a universal cause is compared to a universal effect, and a singular cause to a singular effect: as we say that a builder is the cause of a house, and this builder of this house.

It should also be known that, in speaking of the intrinsic principles, namely matter and form, there is sameness and difference of principles according to the sameness and difference of the things principled. For some things are the same in number, as Socrates and "this man" with Socrates pointed out; some are diverse in number and the same in species, as Socrates and Plato, who though they agree in the human species yet differ in number. Some, however, differ in species but are the same in genus, as man and ass agree in the genus animal; while some are diverse in genus but are the same only according to analogy, as substance and quantity, which do not agree in any genus but agree only according to analogy: for they agree only in this, that each is a being, and being is not a genus, since it is predicated not univocally but analogically.

For the understanding of this it should be known that a thing is predicated of many in three ways: univocally, equivocally, and analogically. That is predicated univocally which is predicated according to the same name and according to the same account, that is, definition, as animal is predicated of man and of ass: for each is called animal, and each is an animated sensible substance, which is the definition of animal. That is predicated equivocally which is predicated of some things according to the same name and according to a diverse account, as dog is said of the barking dog and of the heavenly Dog, which agree only in the name and not in the definition or signification; for what is signified by the name is the definition, as is said in Book IV of the Metaphysics. That is said to be predicated analogically which is predicated of many whose accounts are diverse, but are attributed to one same thing, as healthy is said of the body of an animal and of urine and of a potion, but it does not signify altogether the same in all: for it is said of urine as of a sign of health, of the body as of its subject, of the potion as of its cause. Yet all these accounts are attributed to one end, namely health.

For sometimes things that agree according to analogy, that is, in proportion or comparison or agreement, are attributed to one end, as is clear in the example just given; sometimes to one agent, as doctor is said both of him who acts through the art and of him who acts without art, as an old woman, and also of instruments, but by attribution to the one agent which is medicine; sometimes, however, by attribution to one subject, as being is said of substance, of quality and quantity and the other predicaments: for the account by which substance is a being is not altogether the same as that by which quantity and the others are, but all are so called from the fact that they are attributed to substance, which is the subject of the others. And therefore being is said priorly of substance and posteriorly of the others; and therefore being is not the genus of substance and quantity, since no genus is predicated priorly and posteriorly of its species, but it is predicated analogically. And this is what we said, that substance and quantity differ in genus but are the same by analogy.

Of those things, therefore, which are the same in number, the form and matter are the same in number, as of Tully and Cicero; of those, however, which are the same in species but diverse in number, the matter and form too are not the same in number but in species, as of Socrates and Plato. And likewise of those which are the same in genus, the principles too are the same in genus, as the soul and body of an ass and a horse differ in species but are the same in genus. And likewise of those which agree only according to analogy, the principles are the same only according to analogy or proportion. For matter and form and privation, or potency and act, are the principles of substance and of the other genera; yet the matter of substance and of quantity, and likewise the form and privation, differ in genus, but agree only according to proportion in this, that as the matter of substance stands to substance in the character of matter, so the matter of quantity stands to quantity. Yet as substance is the cause of the rest, so the principles of substance are the principles of all the others.