Philosophy of Nature: III. The Four Causes
B: Formal Cause
Formal Cause
According to hylomorphism, each and every individual material substance is composed not only of matter, but also substantial form. Substantial form is the correlative principle of actuality to the principle of potentiality (matter) whenever a new substance is generated or corrupted from prior substances. In our foregoing account of the material cause, prime matter, we have already indicated how substantial is an intrinsic cause of material substances correlative to prime matter. Form is the principle of determination which accounts for each thing being the kind of thing it is. As matter is the principle of potentiality, of the ability to become other than it is, form is the principle of actuality, of the thing being the sort of thing it is. In natural things, the substantial form is specifically the same for all members of the same species. That is, the substantial form of a thing accounts for it being the sort of thing it is, for belonging to the species to which it does belong. Thus, substantial form, considered apart from any matter in which it resides, is universal. Although form connotes shape or configuration, Aristotle means by form something more.
But in the case of living things, it is very clear that to explain behavior we must refer not to surface configuration, but to the functional organization that the individuals share with other members of their species. This is the form; this, and not the shape remains the same as long as the creature is the same creature. The lion may change its shape, get thin or fat, without ceasing to be the same lion; its form is not its shape, but its soul, the set of vital capacities, the functional organization, in virtue of which it lives and acts…. A corpse has the same shape as a living man; but it is not a man, since it cannot perform the activities appropriate to a man ([Parts of Animals] 640b30-641a17). When I ask for the formal account of lion behavior, I am not, then, asking just for a reference to tawny color or great weight. I am asking for an account of what it is to be a lion: how lions are organized to function, what vital capacities they have, and how these interact. And it is this, again, rather than an enumeration of its material constituents, that will provide the most simple, general, and relevant account for the scientist interested in explaining and predicting lion behavior. (cf. PA 641a7-17)[1]
The arrangement of parts is what members of a species have in common; it is the reason that they belong to the same species. The substantial form is the cause of this arrangement; and as we will examine more closely in the next chapter of this Overview, the soul is the substantial form for living things. Aristotle and Aquinas, thus, are not a reductive materialist in that they believe that things cannot be reduced to their atomic constitution. Rather, they appeal to the Formal Cause to account for the reason the material constituents are arranged as they are.
However, to say that the form is the configuration of parts, does not capture all that Aristotle means by form. While it is true that there can be no form without matter, and in a certain sense, form is realized in matter in a certain configuration (proximate matter), the matter all by itself does not account for its configuration. As we have indicated above, a favorite example of Aristotle’s is the case of a house made out of bricks. The bricks are the matter of the house, but bricks all by themselves do not account for the house, as opposed to a pile of bricks. The form is a cause in the sense that it is constitutive of the thing it is the form of, just as the matter, in a different sense, is constitutive of the thing. But form has a certain priority and explanatory value because the form accounts for the matter being in a certain configuration while in that configuration, something that matter cannot do.
Matter, indeed, is called the cause of the form, insofar as there is no form except in matter. Likewise, the form is the cause of the matter, insofar as matter does not have existence in act except through the form. For matter and form are spoken of in relation to each other, as is said in the second book of the Physics. They are also spoken of [in relation] to the composite, just as the part [is spoken of in relation] to the whole and as the simple [is spoken of in relation] to the composite.[2]
One must remember that the particular material substance is what exists per se, in its own right, and that both its matter (proximate and ultimately prime matter) and its substantial form, are principles, real principles, that account for the substance generating out of, or corrupting into, other particular material substances. Each particular material substance is a real composite of prime matter and substantial form, but properly speaking, the composite is generated and corrupted, but each component principle neither is generated nor corrupted. Each material substance is what it is due to its substantial form. As the principle of actuality, substantial form makes a material thing to be a substance, i.e., a substance of a certain sort. As Aquinas explains, “The form of the natural body is … that by which the thing is.”[3] Elsewhere, he writes, “For the form is that through which a thing is the very thing that it is.”[4]
As substantial form is the principle of a particular material thing being the kind of thing that it is, so is it the principle of unity.
A substance … possesses a single existence and a single principle of operation in virtue of its one substantial form. It is therefore called “one as such” (unum per se).[5]
Furthermore, as we saw earlier in considering whether the material from which a given substance was generated (or ‘mixed’), a difference in operation or intrinsic powers and properties indicates a difference in kind for substances. When water behaves differently with distinct intrinsic powers and behaviors from either hydrogen or oxygen, and salt acts in characteristic ways distinct from sodium and chlorine, these observational facts indicate that these elements and chemical compounds are distinct kinds of substances due to different substantial forms actualizing the potency of prime matter. As we saw earlier, the proximate matter for the generated substances no longer exist since the generated substance behaves in fundamentally different ways from the elements they were made from. Such elements
are present virtually rather than actually, and cannot be actually present given that the properties that flow from their essences or substantial forms are not present.[6]
Thus, substantial form is the fundamental principle of the inherent operation of each kind of thing. And as each thing’s unity in being and operation are determined by the sort of thing each is, i.e., by its substantial form, so is the identity and continuity in being determined by the same substantial form.
[A] material substance’s identity is determined by its substantial form, which grounds its characteristic properties, powers, operations, and the like. But a substantial form is in turn instantiated in matter, and it is the form of a particular individual substance precisely because it informs a particular parcel of designated matter. … It is because a thing’s substantial form determines its identity that it remains the same substance over time despite the loss and acquisition of matter.[7]
Although a given material substance may take on and shed different amounts of (proximate) matter, it nevertheless continues to be the same substance (which it would not if reductive materialism were true) due to it having continuously one and the same substantial form. This is most important, as we will see in the next chapter, in the case of living material substances (plants, animals, and human persons) where their substantial form is their soul (for each kind of thing they are).
Since the formal and material causes together constitute the composite material substance, Aquinas calls them intrinsic causes and distinguishes them from the other two (of Aristotle’s four) causes, efficient and final, which lie beyond what changes, but nevertheless, are in their separate ways what bring about and explain motions and changes.
Matter and form are said to be intrinsic to the thing because they are constituent parts of the thing; the efficient and final causes are said to be extrinsic because they are outside the thing.[8]
We turn next to the third of Aristotle’s Four Causes, the efficient cause, after which we will discuss final causes in the last section.
[1] Martha Nussbaum, ed., Aristotle’s De Motu Animalium, Essay 1, (Princeton: Princeton University Press, 1978) p. 71.
[2] On the Principles of Nature, c. 4.4
[3] ST Ia, q. 45, a. 8.
[4] Disputed Questions on the Soul, Q. 9, co.
[5] Dodds, Philosophy of Nature, p. 52.
[6] Feser, Scholastic Metaphysics, p. 230.
[7] Ibid., p. 268.
[8] On the Principles of Nature, c. 3.3.
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