Philosophy of Evolution: Hylemorphism

The Thomistic Foundations


St. Thomas Aquinas is helpful in treating hylemorphism in the philosophy of nature. 


The problem of the origin of life has given rise in the last centuries to a debate between the Mechanicists and the Vitalists. The problem was not confronted directly or explicitly by St. Thomas.54 However, the solution lies in the Aristotelian doctrine of Hylemorphism which St. Thomas did endorse and explain: "Even in spiritual substances, or angels, there is a composition of act and potency (only God is pure act). In fact, when two elements are found in a thing, of which one complements the other, the relation of one to another is like the relationship of potency to act. Now, in a created intellectual substance are found two elements, that is essence (substantia) and existence, which is not the essence itself: existence is the complement of the existing essence, because each being is in act in so far as it has existence. It remains therefore that in every so called substance there is a composition of act and potency" (Aquinas Summa Contra Gentiles 2. 53).55

Does St. Thomas think that "to live" is an operation like to see, to think, or to feel, or is "to live" a mode of being for St. Thomas? It is a mode of being, because the proper function of the vital form is the immanent regulation of lower activities, an "in-formation." St. Thomas says, "To live for living things is to be" (Aquinas In De Anima 1. 1. 16)56.

Does St. Thomas hold, contrary to Hylemorphism, that prime matter (ens quo) can exist without form (be an ens quod), or even exist ahead of substantial form? No, St. Thomas holds the hylemorphic theory. St. Thomas holds, that it would be absurd "to say that matter could exist before form and without form, for that would be to say that it is being in act without act, a clear contradiction" (Aquinas Summa Theologiae 1. 66. 1).57 Hence prime matter is not nothing, it is a reality, although it cannot be conceived except by reason of its relation to its exigency to form. Even when actuated by a form it is a privation of all other corporeal forms.

Does St. Thomas view matter as the principle of individuation, which determines "this" creature and its species. St. Thomas holds: "It must be said that those things which differ in number in the genus of substance, not only differ accidentally, but also in form and in material. But if it is asked whence these forms differ from one another, there is no other reason except because the difference is in the signate material. Nor is there found another reason why this material is divided from that material, unless because of quantity. Therefore material subject to dimensions is understood to be the principle of this diversity" (Aquinas De Trinitate 4. 2. ad 4).58

At such time that there is sufficient empirical evidence for the "fact’ of evolution, St. Thomas gives the ontological picture in the philosophy of nature. There is no opposition between Hylemorphism, Creationism and evolution. St. Thomas notes that prime matter is in potency to acquire a form, which is a metaphysical tendency. There can be successive acquisitions of form. If the temporal dimension is added, this potency to acquire a form is an evolutionary tendency.59


Author:  John Edward Mulvihill, S.T.D., D.Min., Ph.D.
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