This oeuvre de jeunesse covers a great deal of Aristotle’s natural philosophy, at least in its initial steps. Doubtless its intended reader came away from it with a mind more furnished than it had been before. What the work lacks is dialectical subtlety. In a way significantly different from most of his writing, Thomas does not here stress how one arrives at the position of Aristotle that he is laying out for his reader. We do not have a lively sense of the questions to which these are answers, and although a reader would be able to respond catechetically to questions about Aristotelian hylomorphism it is doubtful that he would be able to defend the answers. This is noteworthy because it is so uncharacteristic of Thomas’s style, philosophical or theological. Perhaps the dialectical atmosphere of Paris had not yet put its stamp upon him.
1
Note that sometimes a thing can be although it is not, whereas sometimes a thing simply is. That which can be is said to be potentially; that which already is is said to be actually. But existence is twofold, namely essential or substantial existence: for example, when a man is, this is to be simply speaking; but there is also accidental being, as when a man is white, and this is to be only in a secondary sense.
Something can be in potency to either kind of existence, as sperm and menstrual blood are potentially man, and a man is potentially white. Both that which is potentially a substantial being and that which is potentially some accidental being can be called matter, as sperm is the matter of man and man is the matter of whiteness, but they differ in this that the matter which is in potency to substantial being is called the matter from which, and that which is in potency to accidental being is called the matter in which.
Again, properly speaking, what is in potency to accidental being is called a subject, while what is in potency to substantial being is properly called matter. A sign that what is in potency to accidental being is called a subject is the fact that accidents are said to be in a subject, whereas substantial form is not said to be in a subject. Matter differs from subject in that the subject does not receive existence from that which advenes to it, but has complete existence in itself, as man does not receive existence from whiteness. Matter however has existence from that which advenes to it; of itself it has incomplete existence. Thus, simply speaking, form gives existence to matter, but the subject [gives it] to accident. Sometimes, however, these terms are used interchangeably, matter for subject, and vice versa.
Just as anything that is in potency can be called matter, so anything from which something has existence, whatever kind of being it is, whether substantial or accidental, can be called form: man when he is potentially white comes to be actually white through whiteness, and sperm when it is potentially man becomes man actually through the soul. And because form causes a thing to be in act, form is said to be act, but substantial form causes actual substantial existence, and what causes actual accidental existence is called accidental form.
Because generation is motion towards form, two kinds of generation respond to two kinds of form. Generation, simply speaking, involves substantial form; and generation in a secondary sense involves accidental form. For when substantial form is introduced, something is said to come to be simply speaking; but when accidental form is introduced, we do not say that something comes to be simply but becomes this. When a man becomes white, we do not say that a man comes to be or is generated, but we say he comes to be white. Two kinds of corruption answer to these two kinds of generation, namely, absolute corruption and corruption in a secondary sense. Generation and corruption simply speaking are only in the genus of substance, but generation and corruption in a secondary sense are in the other genera.
Generation is a kind of mutation from non-being or non-existence to existence or being, and conversely corruption is a change from existence to non-existence. However, generation does not come about from just any non-existence, but from the non-being which is potentially being, as the idol comes to be from a bronze which is potentially, although not actually, the idol.
Three things are required if there is to be generation: being in potency, which is matter, and not-being-in-act, which is privation; and that through which it becomes actual, namely form. When the idol comes to be from bronze, the bronze which is potentially the form of the idol is matter, whereas to be unshaped or indisposed is called privation; the shape by which it is called an idol is form, although not substantial form, because bronze has actual existence before the arrival of form or figure, and its existence does not depend on that shape which is an accidental form. All artificial forms are accidental, for art only operates on that which is already constituted and exists complete by nature.
2
There are three principles of nature: matter, form and privation. Of these one, namely form, is that towards which generation is aimed, while the other two are on the side of that from which generation is. Hence matter and privation are the same in subject but differ in account, for it is the same bronze that is unshaped before the coming of form, but in one account it is bronze and in another unshaped. Hence privation is not said to be a per se principle but per accidens, because it coincides with matter. Similarly we say ‘The doctor builds’ is per accidens, since it is not as a doctor that he builds, but as a builder, and it just happens that the same man is both physician and builder.
But accidents are of two kinds: namely necessary, which is inseparable from the thing, as risible is a necessary accident or property of man; and non-necessary, which is separable, as white from man. Hence although privation is an accidental principle, it does not follow that it is not necessary for generation, because matter is never denuded of privation: for insofar as it is under one form, it is in privation of another, and conversely – as in fire there is a privation of air, and in air the privation of fire.
Notice too that although generation is from non-being, we say not that negation is a principle but that privation is, because negation is not determined to a subject: ‘does not see’ can be said even of non-beings, as in ‘The chimera does not see’, as well as of beings that by nature have no sight, like rocks. But privation of a form is found only in a subject that by nature has that form, just as only things that see by nature are called blind.
Because generation does not come to be from non-being absolutely, but from a negation in some subject, and not in just any subject but in a determinate one – for it is not from just any non-fire that fire comes to be, but from a non-fire that is such that it can come to be the form of fire – therefore privation is said to be a principle. But it differs from the others in that they are principles not only of coming to be but also of being: in order for an idol to come to be there must be bronze, and its ultimate shape must be that of the idol; moreover, once it is an idol, these two must continue to be as its constituents. Privation, however, is a principle only of becoming and not of being: in order for an idol to come to be, it is necessary that the idol not already exist, because if it already were it would not come to be, since what comes to be does not exist save successively, as in time and motion. But that because of which it is now an idol, is not the privation of idol, because affirmation and negation are not simultaneous, nor are privation and possession.
Again, privation is a per accidens principle, as was set forth above, but the other two are per se principles.
From what has been said, it is therefore evident that matter differs from form and privation in definition. For matter is that in which form and privation are understood to be, as shaped and unshaped in bronze. Sometimes indeed matter is understood as in privation and sometimes not, as bronze when it is the matter of the idol does not imply privation, because by ‘bronze’ we do not mean the unshaped and unconstructed, whereas flour when it is the matter of bread implies the privation of the form of bread, because by ‘flour’ I mean something that lacks the form of bread. Matter or subject endures in generation, but not the privation or the composite of matter and privation; it is of course matter which does not imply privation that endures, privation is transient.
But notice that sometimes matter itself is composed with form: bronze is the matter of the idol, but is itself composed of matter and form. Therefore bronze is not called prime matter, because it itself has matter. Matter understood as without any form and privation, but subject to form and privation, is called prime matter, because prior to it there is no other matter, and it is also called Hyle. Because every definition and every cognition is through form, prime matter cannot be known or defined in itself, but only by comparison, as when it is said that prime matter is to all forms and privations as bronze is to the shape of idol and the lack of it, and it is called absolutely first. Something can also be called prime matter with respect to a given genus, as water is the matter of liquids, but not prime matter absolutely, because it is composed of matter and form and thus has a prior matter.
Neither prime matter nor form, it should be understood, is either generated or corrupted, because every generation is to something from something, and the from-which of generation is matter, and the to-which form. If matter or form were generated, therefore, there would be matter of the matter and form of the form and so on to infinity. Thus generation, properly speaking, is only of the composite.
Prime matter is said to be numerically the same in all, but numerically the same is said in two ways. First, that which has numerically one determinate form, like Socrates; prime matter is not said to be numerically one in this way, since it has no form. Second, something is also said to be numerically one because it is without the dispositions that make things differ numerically. This is the way that prime matter is said to be numerically one, because it is understood without any of the dispositions from which numerical difference arises.
And notice too that matter does not include any form or privation in its nature, any more than bronze includes in its notion either shaped or unshaped, although prime matter is never devoid of form and privation, for sometimes it is under one form, sometimes under another. Prime matter can never exist just as itself because, since it does not include form in its notion, it cannot actually be. A thing is actual thanks to form, but prime matter exists only potentially, which is why nothing actual can be said to be prime matter.
3
From what has been said, it is clear that there are three principles of nature, matter, form and privation, but these are not sufficient for generation. What is in potency cannot bring itself to actuality, as the bronze which is potentially an idol does not make itself to be an idol, but needs an agent to bring the form of the idol from potentiality to act. The form does not bring itself from potency to act: I mean the form of what is generated, which we call the term of generation, for the form is only in that which has come to be, but while it is being made it is in becoming, that is while the thing comes to be. Therefore besides matter and form there must be a principle which acts, and this is called the effecting or moving agent or that whence motion begins.
Because, as Aristotle says in Metaphysics 2, whatever acts acts only by intending something, there must be a fourth thing, namely, that which is intended by the agent, and this is called the end. Every agent, both natural and voluntary, acts for the sake of an end, though it does not follow that every agent knows the end or deliberates about it. Only those things whose actions are not determined, but are open to an outcome and its opposite, as in the case of voluntary agents, need to know the end. They must know the end by which they determine their acts. But the actions of natural agents are determined, so it is not necessary to choose the things which are for the end.
Avicenna gives the example of a zither player who does not need to deliberate about each striking of the chords since the movements are determined for him, otherwise there would be delay between strikings and disharmony would result. Since the voluntary agent, not the natural agent, deliberates, it can be argued that if a voluntary agent sometimes acts without deliberation then a fortiori the natural agent can act for an end without deliberation. This intending is nothing other than the natural inclination to something.
It is clear from what has been said that there are four causes, namely the material, the efficient, the formal and the final. However, although principle and cause are interchangeable, as is said in Metaphysics 5, Aristotle in the Physics posits four causes and three principles. By cause he means both extrinsic and intrinsic accounts: the material and the formal are said to be intrinsic to the thing because they are constitutive parts, whereas the efficient and final are called extrinsic because they are outside the thing. Aristotle calls only intrinsic causes principles here. Privation is not listed among the causes, however, because it is an accidental principle, as has been said. When we say four causes, this should be understood to mean four per se causes. Accidental causes are reduced to these, since whatever is incidental is piggy-back on that which is essential.
Although Aristotle means intrinsic causes by principles in Physics 1, still, as is said in Metaphysics 11, the term ‘principle’ is properly used of extrinsic causes, ‘elements’ of causes which are parts of the thing – namely intrinsic causes – and ‘cause’ of both. Sometimes, however, they are used interchangeably, for any cause can be called a principle and any principle a cause. But cause seems to add something to principle as commonly used, because what is first, whether or not any further being follows on it, can be called a principle, as the artisan is called the principle of the knife, but when something is moved from black to white, the black is said to be the principle of that motion, and generally that from which a motion begins is called a principle, but blackness is not that from whose existence the existence of what comes later, that is, whiteness, comes. But cause is said only of that prior thing from which the later being follows; hence a cause is defined as that from whose being another follows. That from which motion first begins to be cannot be called a cause per se, though it is called a principle. On this account privation is numbered among principles but not among causes, because privation is that from which generation begins, but it can also be called a cause per accidens, insofar as it is coincident with matter, as was set forth above.
Only those causes of which the thing is composed are properly called elements, but again this is so not just of any material, but only of that which is first in the composition – a man’s limbs are not his elements, because they are composed of other things, but we call earth and water elements because they are not composed of other bodies, rather natural bodies are first composed of them. Thus Aristotle in Metaphysics 5 (1014a26 – 27) says that ‘the element is that of which things are first composed, and remains in them and is indivisible into things different in kind’.
The meaning of the first part of the sentence, ‘that of which things are first composed,’ is clear from what we have said. The second, ‘and remains in them’, is meant to distinguish elements from that matter which is completely corrupted through generation. As bread is the matter of blood but blood only comes to be when bread ceases to be, so bread does not remain in the blood, whereas elements must in some way remain and are not corrupted, as is said in On Generation .1 The third part, ‘is indivisible into things different in kind’, is meant to distinguish elements from those things which have parts diverse in form, like hand, whose parts are flesh and bones, which are specifically different. But the element does not have parts of different species: every part of water is water. For the being of the element does not require that it be quantitatively indivisible; it suffices that it is not divisible into parts of different kinds. If it is not so divisible, it is called an element, as letters are the elements of words. It is clear then that in some ways principle is found in more things than cause, and cause in more than element, which is what the Commentator says in Metaphysics 5.
4
Having seen that there are four kinds of cause, we should note that a thing can have a plurality of causes, for example, both bronze and the artisan are causes of the idol, but the artisan as the efficient cause and bronze as the material. Nor is it impossible that the same thing should be the cause of contraries, as the pilot is the cause of the safety of the ship and of its sinking, the one by his presence, the other by his absence.
Note too that it is possible for the same thing to be cause and caused with respect to the same, though differently: as taking a walk is the cause of health as efficient cause, but health is the cause of taking a walk, as its end, for one sometimes takes a walk for the sake of health. So too body is the matter of soul, but soul is the form of body. The efficient cause is said to be so with respect to the end, since the end can only actually be attained by the activity of an agent, but the end is said to be the cause of the agent that acts only with the intention of achieving the end. Hence, the efficient is the cause that the end is – that health might be – but it does not make the end to be end – that is, it does not cause the end to be final: just as the physician causes health actually to be, but he does not make health to be an end. For the end is the cause of that which is efficient, that is, the cause that the efficient is efficient – health doesn’t cause the physician to be a physician: I mean the health that comes to be as the result of the physician’s activity – but it causes the physician to act. The end, consequently, is the cause of efficient causality and makes the efficient cause efficient; similarly it makes matter to be matter and form to be form, since matter receives form thanks to the end, and form only perfects matter because of the end. That is why the end is called the cause of causes: it is the cause of the causality of the other causes.
Matter is said to be the cause of form insofar as form exists only in matter, and similarly form is the cause of matter in that matter has actual being only through form: matter and form are correlatives, as is said in Physics 2. They are to the composite as parts to whole and simple to complex.
Because every cause as cause is naturally prior to what it causes, it should be noted that ‘prior’ is said in two ways according to Aristotle, in On the Generation of Animals,1 and because of this both cause and effect can be said to be prior and posterior to the same thing. One thing is said to be prior to another in generation and time, on the one hand, and in substance and perfection, on the other. Since then nature’s operation is from imperfect to perfect and from incomplete to complete, the imperfect is prior to the perfect with respect to generation and time, but the perfect is prior from the point of view of completion. Thus it can be said that man is prior to boy in substance and completion, but the boy is before the man in generation and in time.
Although in generable things the imperfect is prior to the perfect and potency prior to act, given the fact that a thing first exists imperfectly and potentially and then perfectly and actually, simply speaking the actual and perfect are prior, because what brings the potential to actuality is actual and what perfects the imperfect is the perfect. For matter is prior to form in generation and time, as that to which something comes is prior to what comes, but form is prior to matter in perfection, because matter is only completed through form. Similarly, the agent is prior to the end in generation and time, since it is from the agent that the motion to the end comes about, but the end is prior to the efficient cause in substance and completion, since the action of the efficient cause is completed only by the end. These two causes, then, the material and the efficient, are prior with respect to generation, but the formal and the final causes are prior with respect to perfection.
It should be noted that there are two kinds of necessity: absolute and conditional. Absolute necessity arises from causes prior in the way of generation, namely matter and the agent, just as the necessity of death comes from matter’s disposition to join with contraries. This necessity is called absolute because it has no impediment: and it is also called the necessity of matter. Conditional necessity arises from causes posterior in generation, namely form and end, as we say that conception is necessary if a man is to be generated. This is conditional because for this woman to conceive is not absolutely necessary, but under a condition: if a child is going to be born. This is called the necessity of end.
Three of the causes – namely, form, end and agent – can coincide in one thing, as is clear in the generation of fire: fire generates fire, so fire, insofar as it generates, is the agent; it is also the form, insofar as it makes what was potential to be actual; and it is the end, insofar as it is intended by the agent and the activities of the agent terminate in it.
But end is of two kinds, namely the end of generation and the end of the thing generated, as is clear in the making of a knife: the form of the knife is the end of generation, but cutting, which is the work of the knife, is the end of the thing generated, namely, the knife. It is the end of generation not of the generated that coincides with the two other causes in the manner explained – namely, whengeneration comes from something specifically the same, as man generates man, and olive generates olive.
Notice that end and form can be numerically the same, since the end of generation is the form of the generated. The efficient cause is not numerically but only specifically the same: it is impossible that the maker and the made be numerically identical, though they can be of the same species. When a man generates a man, the generator and generated are numerically diverse but specifically the same. Matter does not coincide with the others because matter, by the fact that it is potential being, has the note of the imperfect; whereas the other causes, since they are in act, have the note of the perfect, and the perfect and imperfect cannot be identical.
5
Having seen that there are four causes, efficient, material, formal and final, we should note that each of these causes can be divided into many modes. For a cause can be called prior or posterior; for example, when art and the physician are given as causes of health, art is a prior and physician a posterior cause, and so too with the formal and other causes. Note that we ought always to take the question back to the first cause. When it is asked, ‘Why is he healthy?’, the reply should be, ‘Because the physician cured him,’ and to ‘Why did the physician cure?’ ‘Because he had the art of curing.’
Notice that proximate cause is the same as posterior, and remote cause the same as prior, hence these two modes of cause, prior and posterior and proximate and remote, come to the same. It should be observed that it is always the more universal cause that is called remote and the more specific proximate, as we say that the form of man is his proximate definition, namely mortal rational animal, but that animal is more remote, and substance remoter still. All higher forms are forms of the inferior. Similarly the proximate matter of the idol is bronze, but the remote is metal, and still more remote is body.
Some causes are per se and others accidental. A per se cause is a cause of the thing as such, as the builder is the cause of the house and wood is the cause of the stool. The accidental cause is that which attaches to the per se cause, as when we say, ‘The grammarian builds.’ The grammarian is said to be the accidental or incidental cause of the building insofar as the builder happens to be a grammarian. And so too with the other causes.
Again, some causes are simple, others complex. A cause is said to be simple when only the per se cause is assigned or only the accidental cause, as when we say that the builder is the cause of the house or that the physician is the cause of the house. It is complex when we give them both together and say, ‘The physician builder is the cause of the house.’ According to Avicenna, a cause which is without the addition of anything else can also be called simple, as bronze is the cause of idol since without the addition of any other matter bronze is the matter of the idol; so too when we say that the physician cures or that fire warms. When it is necessary for several things to come together for there to be a cause then it is complex, as when several men, not just one, are necessary to sail the ship, or when many bricks, not one, are the matter of the house.
Again, some causes are actual, others potential. The actual cause causes the actual thing, as the builder when he builds, or bronze when the idol is made of it; the potential cause is that which, although it does not actually cause the thing, can do so, as the builder when he is not building. And it should be noted that, as regards actual causes, the cause and the caused must exist simultaneously, so that if the one is, the other is: for if one is an actual builder, it is necessary that one build, and if actual building takes place, there must be an actual builder. But this is not necessary with causes that are only potential.
Notice that the universal cause is referred to the universal effect and the singular cause to the singular effect: as we say that the builder is the cause of the house, and that this builder is the cause of this house.
6
Speaking of intrinsic principles, namely matter and form, it should be noticed that the similarity or difference of principles is based on the similarity or difference of what follows from them. For some are numerically the same, as Socrates and ‘this man’, point to Socrates; others are numerically distinct but specifically the same, like Socrates and Plato, who though they are alike in the human species none the less differ numerically. Others are specifically different but generically the same, as man and ass agree in the genus animal; others are generically different and the same only according to analogy, like substance and quantity, which do not agree in any genus but are alike only according to analogy: for they agree only in being, and being is not a genus, because it is not predicated univocally but analogically.
To understand this it must be understood that something is predicated of many in three ways: univocally, equivocally and analogically. That which is predicated according to the same name and the same account – that is, definition – is predicated univocally, as animal of man and ass, for both are called animal and both are animate sensible substance, which is the definition of animal. When the same term is predicated of several things according to different meanings it is predicated equivocally, as dog of the barking beast and of a celestial body, which agree in name only and not in definition or meaning: that which is signified by the name is the definition, as is said in Metaphysics 4. Something is predicated analogically when it is predicated of many things whose accounts differ but are attributed to one and the same thing, as when healthy is said of the body of an animal, of urine and of a potion: it does not signify the same thing in all of them, for it is said of urine as the sign of health, of the body as the subject of health, and of the potion as the cause of health. But all these definitions refer to one end, namely to health.
Some things which agree according to analogy, namely in a proportion or comparison or agreement, are attributed to one end, as is clear from the foregoing example, but sometimes to one agent, as medical is said of one who acts through the art and of one who acts without the art, like an old wife, and also of the instruments, but by attribution to one agent, which is the art of medicine; and sometimes, things which agree insofar as they can be attributed to one subject, as being is said of substance, quality and quantity and the other categories, though it is not with wholly the same account that being is said of substance and quantity and the others, but the rest are called beings because they are attributed to substance, which is the subject of the others. Being is said first of substance and secondarily of the others; therefore being is not the genus of substance and quantity, because no genus is predicated of its species according as prior and posterior. Being is predicated analogically. That is what was meant when we said that substance and quantity differ generically but are the same by analogy.
With things that are numerically the same, their form and matter are also numerically the same, as with Tullius and Cicero; of things specifically the same but numerically diverse, the form and matter are not numerically, but specifically, the same, as with Socrates and Plato. And similarly of those things generically the same, their principles too are generically the same, as body and soul are specifically different in ass and horse, but generically the same. Similarly when things agree only according to analogy, their principles too are the same only according to analogy or proportion. For matter and form and privation, or potency and act, are principles of substance and of the other genera, but they agree only according to a proportion: as the matter of substance is to substance in the account of matter, so is the matter of quantity to quantity. Just as substance is the cause of the others, so the principles of substance are the principles of all the others.