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Responses to Thomistic Evolutionists

Most of Aquinas’s teachings come in the Medieval form known as the “question” (Lat. quaestio). A “question” is like a “chapter” in contemporary writing except that the “question” is narrowly focused on one major theme within the metaphysical system. Each question consists of articles. Each article addresses one specific problem. For example, the question treating the existence of God in Aquinas’s Summa Theologiae consists of three articles: 1. Is the existence of God self-evident? 2. Is it demonstrable? 3. Does God exist? Articles are typically divided in three parts. In the first part, Thomas presents the arguments of his adversaries. In the second part, Thomas presents a response from authority (such as the Holy Scriptures or the writings of the Church Fathers). This is called “sed contra”. Then he develops his own answer to the question of the article. In the third part Thomas responds to the objections from the first part.

In the book Aquinas and Evolution the reader will find no less than eighteen arguments produced by Thomistic evolutionists in order to present Aquinas’s teachings as being compatible with theistic evolution. Here we bring up only four of the arguments-the four that are probably the most commonly adduced by Thomistic evolutionists-and give our answers to them.

Argument 1

Aquinas teaches that God makes some things in the universe directly, but other things indirectly by using natural causes. Thomistic evolutionists say that evolution is reconcilable with Aquinas’s teaching because God uses evolution as a secondary cause of creation. Species are the effect of the natural process of evolution guided by God, who works in this process as the primary cause.


Aquinas indeed teaches divine primary and secondary causation. However, in the first production of things, such as production of different species of plants and animals, no secondary causes could have been involved. In fact, Aquinas knew the argument of contemporary evolutionists, because Avicenna claimed a similar thing. This is why we find a direct answer to this claim in St. Thomas’s writings:

It happens, that something participates in the proper action of another, not by its own power, but instrumentally, inasmuch as it acts by the power of another; as air can heat and ignite by the power of fire. And so some have supposed that although creation is the proper act of the universal cause, still some inferior cause acting by the power of the first cause, can create. [And thus Avicenna and the Master say] that God can communicate to a creature the power of creating, so that the latter can create ministerially, not by its own power. But such a thing cannot be, because the secondary instrumental cause does not participate in the action of the superior cause, except inasmuch as by something proper to itself it acts dispositively to the effect of the principal agent. If therefore it effects nothing, according to what is proper to itself, it is used to no purpose; nor would there be any need of certain instruments for certain actions. Thus we see that a saw, in cutting wood, which it does by the property of its own form, produces the form of a bench, which is the proper effect of the principal agent. Now the proper effect of God creating is what is presupposed to all other effects, and that is absolute being. Hence nothing else can act dispositively and instrumentally to this effect, since creation is not from anything presupposed, which can be disposed by the action of the instrumental agent. So therefore it is impossible for any creature to create, either by its own power or instrumentally—that is, ministerially (S.Th. I,45,5 co).

To make Aquinas’s argument short – no creature can participate in the divine act of creation because no creature is apt for this purpose.

Argument 2

Aquinas teaches there are both intended events and truly chance events. Neither, however, escape divine providence. God uses even the chance events to obtain his goals. Consequently, a Christian can admit an occurrence of chance events without detracting anything from divine omnipotence and omniscience. Apparently the most problematic element of biological macroevolution is that chance events (such as random genetic mutations) are the source of biological novelty necessary for natural selection to work. For this reason many neo-Darwinists write as if evolution is a completely random process and a result of blind forces. This obviously excludes God from evolution. Thomistic evolutionists say that thanks to the Aquinas’s doctrine on chance and providence Christianity can adopt chance in the production of species. God simply uses those chance events to produce biodiversity, which ultimately is not a product of chance alone but of the divine intellect, which uses chance to produce species. The divine activity in this process is not detectable at the level of natural science (biology), but one can see it with the eyes of faith, or on the “deeper” theological level: “God designs with chance.”


This argument confuses the order of creation (the formation of the universe) with the order of providence (God’s provision for his creatures) which follows creation. Aquinas’s doctrine on chance events that do not escape divine providence applies to the order of providence but not to the order of creation. In creation there is no (and can be no) chance at all. Creation comes directly from the divine mind. Chance occurs only when secondary causes are involved. Therefore in creation no chance can occur. Again, this argument of Thomistic evolutionists was known to Aquinas because a medieval philosopher Avicenna taught it. Aquinas responds to his claim (that secondary causes are involved in creation) in the following way:

This cannot stand… because, according to this opinion, the universality of things would not proceed from the intention of the first agent, but from the concurrence of many active causes; and such an effect we can describe only as being produced by chance. Therefore, the perfection of the universe, which consists of the diversity of things, would thus be a thing of chance, which is impossible (S.Th. I,47,1 co).

Thomas makes his point even more explicit when he discusses the origin of new forms. But every natural species is a new separate form. Hence the following applies primarily to the origin of species:

Those things whose distinction from one another is derived from their forms are not distinct by chance, although this is perhaps the case with things whose distinction stems from matter. Now, the distinction of species is derived from the form, and the distinction of singulars of the same species is from matter. Therefore, the distinction of things in terms of species cannot be the result of chance; but perhaps the distinction of certain individuals can be the result of chance (ScG, II,39,3).

What Thomas teaches using metaphysical language, everybody experiences in daily life. For example, when a dog gives birth to puppies we see that the puppies differ from each other. We know the hereditary rules and how different genes determine the features in posterity. But, as Thomas says, “perhaps the distinction of certain individuals can be the result of chance”. When one of the puppies unfortunately gets sick in the womb, it may be born different due to the disease. A random genetic mutation may also make an individual different. So, chance can produce differences between the individuals, but not the difference according to species. All puppies, however diversified, remain dog puppies. They share the same substantial form of a dog, which could not have been produced by chance. This argument of Aquinas goes directly against Thomistic evolutionists’ claim that God created new species using chance.

Argument 3

Some of the better educated Thomistic evolutionists, such as Jacques Maritain and Charles De Koninck, were aware and understood well that an accidental change cannot generate a substantial change—the claim implied by biological macroevolution. In other words, they knew that an entirely new nature or substance could be produced only directly by God. Unfortunately, deluded by the evolutionary vision of the universe and intimidated by the so-called “scientific community,” they chose to tinker with Aquinas’s metaphysics to make it compatible with evolution rather than disprove the “Darwinian metaphysics.” They came to the conclusion that the difficulty of the accidental change resulting in a substantial novelty might be overcome if “substance” were redefined according to the needs of the argument. The task was somewhat easy due to the analogous character of the metaphysical notions of “species” and “substance.” If we take substance in a more abstract sense, they reasoned, we could reduce the number of substances in the universe and the number of substantial changes that are required to produce them. For example, if substance is what is material and rational, there is just one substance of man. If substance is a type of life in matter then there are only three substances – the vegetative, the sensitive and the rational. If substance is a composition of matter and form then there is only one substance in the material universe (because in the material universe everything is composed of matter and form). And if there is just one substance, everything may be produced by evolution because it takes only an accidental change to produce individual beings of the same substance. This is why some Thomistic evolutionists claimed that there is only one substance in the material universe (Maritain), some that there are only three (N. Luyten), and some that there are only four (De Koninck) or five (M. J. Adler). None of these authors bothered to show this idea in Aquinas’s writings.


Owing to the analogous character of the term “substance,” we can indeed speak of one or a few substances in the universe, depending on the level of abstraction we employ. The more abstractly we understand substance the fewer substances there are. However, this is not how the notion of substance can be applied to evolution. Since evolution is about the origin of natural species, one cannot avoid a more specific notion of substance. Surprisingly enough, the problem of reducing the number of substances to make metaphysics compatible with a false theory of nature was already known to Aquinas. For example, Avicebron believed that all material things constitute one substance. By this Avicebron wanted to save his notion of causality, which excluded secondary causation. Avicebron believed that since everything is one, God causes everything by himself, without secondary causes. He strove to save the idea that when fire heats, it is in fact God who heats not the fire, when air pushes it is in fact God who pushes, not the air, etc. For us the relevant point is that Avicebron believed that all material things are one substance. But Aquinas disagrees with him and says that this idea “would make an end of generation and corruption, and many other absurdities would follow.” Thomas also says that this idea is “frivolous” and “manifestly fallacious” (De pot. q.3, a.7 co). When Thomistic evolutionists claim that there are only three, four, or five substances their opinion is also manifestly fallacious, and many absurdities follow, such as that a cat and a dog have the same nature, or that the difference between an elephant and a squirrel is only accidental.

Argument 4

The fourth argument worth discussing here is similar to the first one but introduces an additional premise. Thomistic evolutionists claim that God’s use of secondary causes makes his creation nobler and more worthy. To support this they quote Aquinas:

The perfection of the effect demonstrates the perfection of the cause, for a greater power brings about a more perfect effect. But God is the most perfect agent. Therefore, things created by Him obtain perfection from Him. So, to detract from the perfection of creatures is to detract from the perfection of divine power. But, if no creature has any active role in the production of any effect, much is detracted from the perfection of the creature. (ScG, III, 69).

According to Thomistic evolutionists, it was more fitting for God to have worked via evolution rather than [to have] created all species at the beginning because in doing so, He was able to give His creation—the  material universe and the individual creatures within it—a share in His causality. In this way, He more fully communicates His perfection to His creation more clearly manifesting His glory.


This argument fails at the very start, because there is not (and cannot be) any secondary causation in creation, as explained in the first answer. However, this argument draws on a new premise which implies that evolution as the secondary cause of producing species makes our image of creatures nobler and reveals more of divine perfection. The answer to this premise is twofold.

Firstly, as Aquinas says, if there were no secondary causation in the universe, this would detract much from the perfection of divine power. But secondary causation is better only relatively—compared to no actions of creatures at all. This is what Thomas exactly says in the fragment quoted above: if no creature has any active role in the production of any effect, much is detracted…. However, secondary causation of creatures is not better absolutely, because there are other types of divine causality which are nobler and reveal more of divine power. And this is creation, which has no secondary causes. Aquinas says it numerous times in different contexts. For example:

It is a greater act to make something according to its entire substance, than to make something according to its substantial or accidental form. (S.Th. I,45,3, sc).  (Creation is production of being according to its entire substance. Changes, such as in evolution, produce only accidental forms.)

It is an act of much greater power to make a thing from nothing, than from its contrary. (S.Th. I,45,5 ad2). (Again, creation is production from nothing whereas change, such as evolution, is making a thing from its contrary, i.e., from something that is not-this-thing.)

Although to create a finite effect does not show an infinite power, yet to create it from nothing does show an infinite power. (S.Th. I,45,5 ad3).

Creation is more perfect and excellent than generation and alteration, because the term “whereto” is the whole substance of the thing; whereas what is understood as the term “wherefrom” is simply not-being. (S.Th. I,45,1 ad2). (Again, evolution consists of generation and alteration whereas creation emanates being out of nothing toward its entire substance.)

These and similar statements by Aquinas make it clear that it is creation rather than secondary causation that reveals divine power in the best way. In fact only creation reveals an infinite power, because there is an infinite distance between non-being and being, and only an infinite power can trespass an infinite distance.

Secondly, we need to observe that the argument is formulated as if direct creation was removing secondary causation from creatures. But this is not the case by any means. The fact that God created species immediately does not remove secondary causation from the operations of nature. There was a time of creation in which God worked directly in the natural order, but once creation and formation is finished God still works, but for the most part indirectly and by using natural causes (with the exception of miracles that may be caused either directly by God, or by secondary causes in a way that exceeds the powers of nature). But even in miracles nothing entirely new is created; rather, an existing species is multiplied (e.g., in the multiplication of bread) or restored to its proper state (e.g., in returning sight to the blind). Therefore, production of species directly by God in the beginning does not detract anything from creatures, which are incapable of being secondary causes in creation anyway. The whole Thomistic concept of secondary causation refers to the order of providence (operation of the universe), not to the order of creation. And this is why Aquinas speaks about the necessity of secondary causes when he discusses divine providence, not the origins of the universe. Thomistic evolutionists remain silent over Aquinas’s teachings on creation, though they gladly quote his teachings about providence. But these are two different teachings that get confused in Thomistic evolution.

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