1. Matter, Form, and the Substantial Composite
a) Prime matter. - Aristotle tells the meaning as follows: "Matter I call the primary substratum of each thing, from which a thing comes to be but not as an accident, and which remains throughout." 13 St. Thomas translates Aristotle as follows:
primum subiectum ex quo aliquid fit per se et non secundum accidens, et inest rei iam factae.14
Matter, then, is the primary subject of each natural thing, an essential principle of its generation. Not only is generation, or becoming, grounded in matter, but matter survives the becoming and inheres in the thing that became, even as it had inhered in the previous thing.
Prime matter's essential property, if one may speak of it having a property, is its complete indetermination, which Aristotle in another context describes in these words: "By matter I mean that which in itself is neither a determined thing, nor of a certain quantity, nor designated by the other categories by which being is determined." 15 In Scholastic axiom matter is similarly
neque quid, neque quale, neque quantum, neque aliquid eorum quibus ens determinatur,
that is, neither actual substance, nor quality, nor quantity, nor anything else by which being is determined.
An equivalent and more concise expression of matter's utter lack of determination is "pure potency." Matter is pure potency; hence it is not "being in act" (actual being) but only "being in potency" (potential being) : non est ens actu sed potentia tantum. Matter cannot be actual being, since it is the subject of first act, that act by which a being first becomes actual and receives substantial existence. Were matter in act before receiving a form, it would of itself be a substance, and every supervening act would be no more than an accidental act or form. Once more, then, matter is pure potency. This, without a doubt, is Aristotle's true meaning. It is also the meaning that St. Thomas and his followers were adamant in defending against all who insisted on giving matter a positive determination precedent to form.
If matter is pure potency, then, as Aristotle further observes," matter properly speaking is not "what exists" nor "what is generated" - non quod existit vel quod generatur; it can only be "that by which" - quo - the composite exists. The true subject of existence is the composite of matter and form. It is incorrect, therefore, to think of matter having one existence and form another. Matter and form have the same act of existence.
In itself, moreover, prime matter is said to be "one" in the sense that it does not have actual parts; it is only potentially many. And finally, Aristotle thought matter not only ingenerable but eternal. This notion, eternity, is not essential to matter. Christian thinkers, who knew that matter like everything else was created in time, could abandon this detail without prejudice to the doctrine as a whole.
b) Substantial form. - Like prime matter, substantial form is an intrinsic, nonaccidental principle of mobile being. It is the first act of corporeal or physical substance; which means it is the principle by reason of which this substance exists as well as the principle that causes this substance to be one kind of thing instead of another. As the Scholastic formula tells it, substantial form is "that by which a thing is determined to a certain mode of being":
id quo res determinatur ad certum modum essendi.
Form does not exist alone or by itself, and is not generated. In this it is again like matter. Unlike matter, however, forms are not transmitted in the process of generation from subject to subject; rather, they are drawn - "educed" is the knowledgeable word - from the potency of matter, and matter in turn is actualized by the educed form. One important exception should be noted. Christian metaphysics knows of a form that does not originate by eduction from matter. This is the human soul, which is always created outright by God to be the substantial form of a human body.
Form, we have said, is first act, the act of matter. Form, that is, actuates matter and matter is actuated by form. Yet matter cannot be actuated by more than one substantial form at a time, as the simultaneous plurality of forms would destroy the essential unity of the composite. True, the doctrine of the unicity of form has at various times been hotly contested. But whatever one's stand one thing is agreed. Aristotle, for sure, is all on the side of unicity; and so, with all his mind, is St. Thomas.
c) The substantial cornposite. - From the union of matter and form results the substantial composite, the concrete being we meet in nature. As was said apropos of form, "what exists" - quod existit - in nature is not matter or form taken separately, but the composite of the two. So, to speak precisely, the true principle or subject of substantial corruption (change) is the composite (and not matter or form individually), and the true term of substantial generation (becoming) is another composite. Generation and corruption are reciprocal, one always entails the other; hence the axiom generatio unius corruptio alterius. In every natural generation and corruption it is a composite that is generated (quod generatur) and a composite that is corrupted (quod corrumpitur). Obviously, for this meaning of "corrupt" one must take the literal Latin, "to break up."
Not only is the composite "what exists" or has existence, but the composite (and not form or matter separately) is also the subject in which the accidents inhere. Consequently, all the subject's activities are ultimately said of the whole composite, the ultimate, intrinsic principle of all ac-tivity. Actions, to use the Scholastic phrase, are the supposit's: actiones sunt suppositorum.17
The composite of matter and form is, plainly, one being. Its unity is essential or substantial in contrast to the accidental unity of substance and accident or of accidents with each other. How is this unity effected and sustained? Some past (if not present) Scholastics think that there has to be a coupling principle in the composite to bind matter and form together, but just what this should be is again a focus of controversy. Enough for us to remark that in the mind of Aristotle and St. Thomas no such coupler is called for. Matter and form determine and delimit each other directly; their union, because a union of act and potency, is immediate.
Lastly, we note in passing that form, the determining principle of the composite, is ontologically prior to matter. Though composed of both matter and form, a being of nature is principally form. This notion of form's primacy is of the highest importance not only in Aristotle's doctrine of nature but in his whole scheme of philosophy. More of this in the chapter on nature.18
2. Elements and Mixtures (Compounds)
We have said that corporeal substances are composed, ultimately, of prime matter and substantial form. We have also spoken of second matter and accidental form, which are the immediate principles of accidental change, the change that does not alter the essential being of things. Besides substantial and accidental change, is there any other kind? Strictly speaking, no.
Yet, in De Caelo and De Generatione et Corruptione Aristotle introduces a type of change that seems neither all one nor all the other. This is the change by which "mixtures" or compounds are produced. The basic structure of the bodies concerned (elements) is affected, yet the process does not appear to be a substantial generation pure and simple. Aristotle, in consequence, notes two kinds of natural bodies, elements and mixtures, the former more basic than the latter, but both the work of nature. Elements were thought to transform into each other by clear generation. Mixtures were a fusion of pre-existent elements. Because of its obvious parallel to the modern theory of element and compound the Aristotelian doctrine of element and mixture still merits attention.
a) Elements. - "Element," says Aristotle, "is the first component of a thing, immanent and of a kind that is indivisible into another kind." 19 Or, in St. Thomas' rendition,
elementum dicitur ex quo aliquid cornponitur primo, inexistente indivisibili specie in aliam speciem.20
St. Thomas singles out four points in this definition:
According to Aristotle there are four basic elements in nature: water, air, earth, and fire. This listing was common in his time. To be noted, however, is that the elements were not the water, air, earth, and fire of everyday experience. These, in Aristotle's meaning, were already compound bodies but named, respectively, after the preponderant element or component. So, in this theory water as we see and drink it is a composite in which the element called "water" predominates. Similarly, in the air, earth, and fire of common experience one element overshadows the other (s) and gives its name to the whole.
All the elements had two notable properties. For each there was a natural place toward which it gravitated by an internal force. Fire naturally turned upward and came to rest just below the lunar orbit. Earth moved downward. Air and water shared the intermediate zones. Of these inner thrusts, heaviness and lightness were the outer manifestations.
The other feature was in their qualitative texture, which in each case was a blend of two of the contrary qualities. Assuming the basic qualities of nature to be warm, cold, dry, and wet, Aristotle finds them in the following paired associations with the elements:
These qualities were also the active principles that accounted for the reciprocal alteration of the elements; and when in a given case alteration had reached the necessary point, one element was completely transformed into another by outright, or substantial, generation.
So much for Aristotle's theory of elements. Today many of its finer points are admittedly untenable, though perhaps of interest still to the antiquarian. But this is not to say that its basic insights are similarly dismissible, or that they cannot be integrated with the conceptions of modern science. The modern physicist, to mention one instance, knows of subatomic changes that have all the earmarks of genuine particle-transformation. Surely, this manifestation bears comparison with the transmutation of elements spoken of by the ancients.