Intrinsic Causes
The material cause (prime matter and secondary matter) and the formal cause (substantial form and accidental forms) as the intrinsic determining principles of bodily effects.
The material cause is the matter out of which an effect is made. If the effect is itself a substance, its material cause is prime matter — the common, indeterminate, purely potential substrate of all bodies, neither a definite kind of matter nor nothingness, which can neither exist nor act by itself but receives the substantial form that constitutes a specific bodily substance. If the effect is itself an accident (e.g. a crucifix carved from ivory), its material cause is secondary matter — the actual, existing bodily substance in which the accidental change takes place. The formal cause is a determining cause: that which sets, determines, or marks the effect as this precise kind of thing. The substantial formal cause (substantial form) determines the substantial kind of the effect; accidental formal causes (accidental forms) determine the accidental kind. The causality of matter is receptive, not active; the causality of form is active or, more precisely, actualizing — it in-forms matter and sets it in actual and determinate being.
Article 2. Intrinsic Causes
a) The Material Cause b) The Formal Cause
a) The Material Cause
A material cause is the bodily matter out of which a thing is made. As we have seen, only bodies have a material cause. Spiritual substances (souls or angels) have no material in their make-up, and hence have no material cause.
A material cause is matter. Now, matter is distinguished as primary matter (or prime matter, as it is usually called) and secondary matter. Secondary matter (materia secunda) is a bodily substance as it exists in nature; it is a body constituted in its being and subject to accidental changes. Wax, wood, iron, a piece of coal, a twig snapped from a bush — these are examples of secondary matter. Secondary matter has its own existence; it is an actual thing in itself, a real body. When a bodily substance undergoes accidental change, the material cause of the accidental effect is the secondary matter in which the change occurs. Thus ivory (an existing bodily substance, a secondary matter) is the material cause of the crucifix, which is (as a crucifix, as an image, as a “shaping”) an accidental thing, produced by accidental change. The point is, the ivory was subjected to accidental change only. The substance called ivory was not re-determined in its substance; it remained ivory; it remained substantially unchanged.
Let us now consider the ivory of the crucifix in itself, as a bodily substance. Manifestly this ivory is a finite and hence a contingent thing; in other words, it is an effect. And it is a bodily effect. What then is its material cause? We notice that as a body, ivory has a common element with all other bodies. There is no difference on the score of bodiliness (that is, the fact of being body) between ivory and lead, or silk, or a tree, or a dog, or a man. True, the bodies mentioned are essentially different in the kind of bodies they are, but they are not different in the fact of being bodies. For this common element which is thus discerned in every bodily substance, there must be a real explanation and an accounting. The only satisfactory explanation of the point is one that has stood the test of over two thousand years; it is the doctrine of prime matter as the substantial substrate of all existing bodies.
Prime matter is a substantial reality, but it is not a complete substance. It needs a co-substance before it can have actual existence. For its existence is potential only. Prime matter is purely indeterminate, purely potential. Indeed, it has been defined as pure potentiality. Any simile or analogy is to be studied with caution, for it will necessarily be a very imperfect illustration of what we mean by truly prime or primary matter. Suppose for a moment that the whole bodily universe as we know it is annihilated, and that there exists a great mass of clay. Now, the Divine Power touches this clay, and instantly it is formed into all the different bodies of the universe again. The clay will illustrate (most imperfectly) what we mean by a common substrate of all bodies actually existing — it will illustrate prime matter. Yet the illustration is very weak, because the clay is really a special kind of matter; it has its own existence before the bodies are drawn out of it; it is therefore not primary matter, but secondary matter. For prime matter cannot exist itself; it is no special kind of matter, for its kind comes to it with the substantial determination which sets up secondary matter (that is, with substantial form), and prime matter is wholly without determinations or determinateness. Yet it is not nothingness; nor is it actual (that is, existing) being; it is potential being. To say that it is potential being is to say that it is a capacity, a capability, a possibility, for receiving determining co-substances (that is, substantial forms) which, in each case of union with it, will produce a body, will produce secondary matter.
When you take hydrogen and oxygen in proper proportions and combine the two gases under the action of a suitable agency, the result is water — a new substance which was not there before. You have driven off the substantial determinants that made the gases hydrogen and oxygen; you have brought in the determinant which makes this new substance water. What is the field of this operation? The simple answer is: prime matter. Prime matter is the common ground and substrate of all bodies. It is a capacity for becoming any sort of possible body, and when you fill this capacity in any given case, you actualize the potentiality of matter, and you say that the determinant (or substantial form) which sets the new substance in being is educed from the potentiality of prime matter. At the same moment in which the new substantial determinant or form is educed (and the new body thereby constituted as actual), the old substantial determinants disappear, and are no longer actual; they are said to be reduced to the potentiality of prime matter. Only spiritual forms (souls) are not thus educed and reduced; each is created.
The material cause of the substance called ivory is therefore prime matter. This is the material cause of all bodies considered in their basic substantiality.
b) The Formal Cause
The words form and formal have a wide range of meaning. In casual speech they suggest something rather unimportant, or something superficial, or something merely accidental. Thus we speak of a formal dinner or a formal dance. In flat contrast with this casual usage, philosophy employs the terms form and formal (and formality) as words of tremendous significance.
We may take as the best synonym for form, the word determinant (that is, a reality which sets and determines and marks a being). And for formal, the adjective-participle determining will serve us well. A formal cause is therefore a determining cause. It is a cause which sets, determines, or marks the effect as this precise kind of thing. And the kind may be substantial kind or accidental kind.
When the artist took up a bit of ivory and carved it into the crucifix, he bestowed upon it a new form. He gave it a new determination or determinateness; he bestowed upon it, by his efficient activity, a factor which is a determinant of what it now is. This new form is an accidental form; for the substance called ivory was not re-determined in its substance, was not changed, was given no new form in itself as ivory. The substance remained ivory; it remained substantially unchanged. Yet the accidental form which was given to the ivory as a determination, and which abides with it as a determinant, is a contributing factor in the effect called this crucifix. Had the ivory been shaped differently, by so much as one line, it would not have been precisely this crucifix. Hence, the accidental form of the crucifix has the nature of a true cause. It contributes in some manner to the actual (accidental) being of the effect. Whatever contributes, in any manner whatever, to the determining of what sort or kind of effect is produced, is a true formal cause. Whatever contributes, in the accidental order, to the determining of what kind the effect shall be, is a true accidental formal cause.
Come now to the study of the substance of the water in another example. What makes this water water? As water it is not only a bodily substance, it is a bodily substance of a certain substantial kind. And something determines that kind. That which makes this body (water) a body — not, indeed, an actual or existing body, but a thing with fundamental bodiliness — is prime matter. But that substantial reality which has united with prime matter to constitute this body as an actual or existing body of the precise substantial kind is the substantial form of water. Prime matter is indifferent in itself; it is a capacity for receiving forms, and it can have in itself no tendencies or leanings towards one sort of form rather than another, for it does not have existence in itself. Therefore, any determination, determinateness, or determinant that we discern in a substance as distinct from its mere bodiliness, and as setting it off from other bodies of other substantial kinds, is from a determining co-substance, a substantial form. This form is not from without the substance, not externally, but fundamentally and intrinsically — in a manner that puts the matter itself into actual existence as this actual substance. We call this substantial determination and determinant by the name substantial form. And when we view an existing body as an effect, we say that the substantial form determines this effect in its substantial character as an existing body and an existing body of this substantial kind and no other. In this view, the substantial form is the substantial formal cause.
Matter and form are true causes. They contribute to the production of the effect in its existence and in its essence. They are intrinsic causes, for they constitute the effect; they are right in the effect. The causality of matter is not an active causality, for matter (that is, prime matter) has no existence of its own in which it could exercise causality; even secondary matter is of its nature inert and exercises activities by capacities which are forms. The causality of matter is receptive causality; it is capable of receiving forms, first the substantial form, and through it accidental forms. The causality of the form is an active or actualizing causality, for form unites with matter and in-forms it, thus setting up the substance in actual and determinate being.
Summary of the Article
In this short Article we have made a detailed study of material and formal cause. We have found that the material cause, which has place only in bodily reality, is the matter out of which an effect is made. If the effect is in itself a substance, its material cause is prime matter, the common and indeterminate substrate of all bodies. If the effect is in itself an accident, its material cause is the secondary matter, the actual bodily substance in which the accidental effect takes place or has its being. We have learned that the formal cause is a determining cause, that it determines the kind of thing the effect is, whether this be substantial kind or accidental kind. The formal cause which determines what substantial kind the effect is, is the substantial form of the substance-effect. The formal cause which determines what accidental kind the effect is, is an accidental form inhering in the substance-effect. We have illustrated this doctrine with several examples and analogies. We have seen that the causality of matter is receptive, not active; while the causality of the form is active, or, more precisely, actualizing.