The Dumb Ox on Evolution

Thomism offers a valuable service to mankind by guiding the scientific discussions only in the direction of those theories that have a solid metaphysical foundation.

In a 1996 address to the Pontifical Academy of Sciences, Pope John Paul II said “the Church takes a direct interest in the question of evolution, because it touches on the conception of man, whom Revelation tells us is created in the image and likeness of God.” 1 The Holy Father went on to say “that new findings lead us toward the recognition of evolution as more than an hypothesis.” 2 The challenge that is set before both the Church and the scientific community is how the conclusions regarding the origin of man that are reached through the scientific disciplines can be reconciled with those that are contained in Revelation. “We can all draw profit from the fruitfulness of frank dialogue between the Church and science.” 3 Despite the fact that these two views appear to conflict with each other, we know truth cannot contradict truth, and so a reconciliation is possible. Philosophy based on the teachings of St. Thomas Aquinas can serve as a bridge between these two fields of knowledge.

Although the Pope said that the theory of evolution was “more than an hypothesis,” he never defined the theory itself. In fact, he said it is “more accurate to speak of the theories of evolution” 4 because many of the so-called theories of evolution rest upon a flawed metaphysical theory. Thomism offers a valuable service to mankind by guiding the scientific discussions only in the direction of those theories that have a solid metaphysical foundation. It is instructive, therefore, to examine the metaphysical principles and offer a possible solution that is consistent with both a sound metaphysics, and the current scientific data.

A Third View of Creation

There is a necessary distinction that needs to be made at the outset. As a matter of polemics, a belief in creation is often lumped together with what is commonly referred to in Christian fundamentalist circles as “creationism.” Belief in creation, however, is not the same thing as creationism. Creationism starts with the view that the six days of creation are meant to be taken literally, and then posits that the earth is about 6,000 years old. However, any attempt to prove this scientifically is untenable and is, therefore, summarily dismissed. St. Thomas warns about attempting to invoke arguments like these for “the Christian faith that are ridiculous because they are in obvious contradiction to reason,” and only serve to provoke the irrisio infedelium, the mockery of unbelievers. 5 

Likewise, it is often thought that belief in creation requires that the Creator had to make a perfect and faultless world (we will call those who hold this view “perfectionists”). The only perceived alternative to this is a world based purely on chance. In response to the latter, St. Thomas himself addressed the question as to whether chance could govern the world. In addressing the “atomists” in his time, who saw the variety in the world as the result of a random interplay of matter, he said that the variety is precisely the intention of the Creator. God “brought forth many and diverse creatures, that what was wanting to one in the representation of the divine goodness might be supplied by another. For goodness, which, in God, is simple and uniform, in creatures is manifold and divided.” 6

However, St. Thomas would not come down on the side of the “perfectionists” either. Instead, he would posit that there is a third possibility as an alternative to both of the other viewpoints. This alternative views creation as in the process of becoming. It has a beginning, and is undergoing a process of development that has not yet come to its end.

This third way is based on two metaphysical principles that St. Thomas consistently affirms.  The first is that “every being, as being, is good.” 7 Everything that exists has being, and the fact that it has being makes it ontologically good. This, however, does not mean that everything that exists is the best that it can possibly be. This is relevant to the problem at hand in that, according to St. Thomas, God could have created a better world. 8 Therefore, not everything we find in the world (or even the world itself) is perfect. Secondly, although all being is good, it is limited (allowing, as will be shown, for the possibility of a simple being with no limiting principle). Just as no work of art can express or exhaust everything an artist has to say because it is always limited by its material framework; likewise, no creature can entirely express the Creator. 9 St. Thomas refers to this limitation of the mode of being as “essence.”

Essence and Existence

It is the idea of essence as limiting the mode of being that makes the metaphysical vision of St. Thomas unique. Every real being (again allowing for a possible exception) is constituted by an inner structure of two metaphysical principles. The first is the act of existence by which the being is actively present in the universe of real beings. The second is its limiting essence by which it exists in a particular mode of being, as a particular being, and not another. This creates a natural hierarchy of being. Each being is like every other in that it exists, but it is different in that its essence represents a greater or lesser share in being. In addition to this vertical dimension of being, there is a horizontal dimension as well. There are individual beings which share the same essential form. Just as essence limits the mode of existence, so, too, matter limits the number of individuals that share the same form. 10 This creates a matrix of being in which the vertical dimension (essence/existence) represents differences in kinds (called “ontological”), and the horizontal (“matter/form”) represents differences in degrees.

In addition to the static principles of essence as limiting existence, and matter as limiting form, St. Thomas also describes a dynamic principle of being that governs the process of change through the Aristotelian notion of act and potency. Amidst all the changes in a given being, there must be a principle of continuity that acts as an aptitude to receive a new mode of being. This aptitude is its potency, or potentiality. Potency can be either passive—which is the capacity to receive some actual perfection; or active—which is the capacity to act from within. 11

All too often the notion of a designer (especially those of the “intelligent design” school) is connected with something like a divine engineer who creates some vast, well-oiled machine that operates perfectly. In contrast, the Thomistic understanding would say that creation is not so much a vast machine, but a “republic of natures” as Thomist philosopher Jacques Maritain put it. 12   This means that, in creation, there is, above all, growth and becoming. Creatures reach their goal, or attain their purpose, not from some passive potency, but from an inner force or potency that is governed by their nature, and endowed by the Creator as the way beings shape themselves. 13

Based on Chance?

Clearly, the Thomistic view rejects the notion that all of creation is governed by a random process—but does chance play any role in St. Thomas’ metaphysics of creation? To answer this question, we can apply the “Principle of Sufficient Reason” to change in the universe. 

The “Principle of Causality,” as it is commonly referred to, states that every being that lacks the sufficient reason for its own existence in itself must have an adequate efficient cause. Those who would label themselves as “Evolutionists” often mistakenly quote this principle as “nothing is caused by itself” or “every being requires a cause.” By eliminating the important qualifier (“those that lack being in themselves”), the principle is then quoted as a way to refute the existence of God—because he is just one being among many, rather than Being itself—as he, too, would require a cause. 14

It would seem, then, that any notion of chance would violate the Principle of Causality, and any talk of chance is nonsensical. However, chance can be used in two ways. The first way is when we speak of chance as being really based on some unobserved causality. 15 The second, however, can result from two or more lines of causality, neither of which are governed by chance, but act independently of each other. It is this second meaning of chance that is compatible with an evolutionary world in which chance plays a role. This in no way should be seen as a rejection of the Providence of God in that Divine Providence places necessity on some things and contingency on others. 16 

It seems, then, that the central metaphysical problem related to evolution is how to explain it without violating the Principle of Sufficient Reason, specifically the causal axiom that “no effect can be greater than its cause.” 17 With this in mind, we find that an evolutionary theory based on “naturalism” must also be rejected. This viewpoint claims that nature, in itself, is self-sufficient and, at first glance, seems reasonable, especially because it has room for a deistic conception of God.

Recall what was said above regarding active potencies as the ability to act in some manner innately. Two beings already existing in nature may have the active potentiality to combine with each other, under certain conditions, to form a new being. For example, two hydrogen atoms and one oxygen atom, both of which are flammable, combine to form a water molecule, which has the opposite property of putting out fires. This viewpoint may explain evolution in the pre-biological dimension of our world in which all change may be a change in degree. However, this theory cannot explain those changes that require a step up the ladder of being without violating the Principle of Sufficient Reason. 

A Thomistic Approach to a Solution

A solution to the question of evolution, that is based on an authentically Thomistic approach, would need to conform to the Principle of Sufficient Reason.

This means that it must present creation as containing some points of discontinuities, and cannot be a wholly continuous process that has been set in motion. St. Thomas taught that non-living creation shares in existence to a lesser extent than creation that has life. There is a further division within the realm of living beings. Aquinas presents all living beings as having one of three kinds of souls. These kinds of souls, delineated as vegetative, sensitive, and rational, serve as animating principles for living beings. 18 All living things have vegetative powers in their souls, but only plants have a vegetative soul. Likewise, both man, and the animals, have sensitive powers in their soul, but only animals have a sensitive soul. Only man, with reason and will, has a rational soul. It seems natural to posit that the points of discontinuity would be reflective of these distinctions. A Thomistic theory of evolution then could be developed by dividing the problem into four distinct areas.

The first would be evolution in the non-living universe, from the Big Bang to the formation of the earth. This would be similar to the theory of “naturalism,” discussed above. In order to satisfy the Principle of Sufficient Reason, all that seems to be needed is the infusion of a range of active potentialities (even if they are latent) in the universe. This integration would require an Organizing Intelligence, but would not require any further special intervention of the Creator (although there is room for such an intervention in theory). 19

Secondly, we could speak of the evolution of plant life. The Principle of Sufficient Reason requires that an outside source of causality would be needed to move up the ladder of being, from non-living to living.

Next, we could speak of evolution of sub-human animals. The presence of the sensitive powers must indicate a difference in kind because between the presence of these powers, and the lack, there are no intermediaries possible. Therefore, this suggests that there must be a qualitatively new level of ontological perfection present. 20  

It should be mentioned that the idea of micro-evolution within species presents no special philosophical problem. It may simply be the result of accidental changes, with the same essential nature that produces beings that are different in degree only. Many scientists have posited that these accidental changes could be brought about by an active potentiality that consists in gene jumping in response to a given environment. 21 This may, in fact, become so cumulative, that the later entities are no longer able to breed with the earlier and, thus, a new species is judged. This, however, does not imply a qualitatively new level of ontological perfection. Any jumps there are need to be explained. It seems that the only plausible metaphysical explanation would be to see creation as a continuing, ongoing activity of an intelligent being who infuses new active potentialities into creation at critical points in the process. 22 

Finally, we come to the final step, which is the evolution of man. Once again, we find that man represents a jump on the ontological ladder through the spirituality of the human soul. The ability to form abstractions is attributed to man, along with propositional speech, tool-making for future use, and cumulative culture, all marking a transcendence of the immediate environment. These powers cannot be explained by combining material causes, and require an outside, non-material cause. 23


In his essay, entitled “The Timeliness of Thomism,” Josef Pieper said that the “never-ending task of the true teacher (is) to reflect the totality of truth and, in a constantly inquiring meditation, to discover and point out wherein lies the relevance of truth to his own time.” 24 When applying this to the question of evolution, we do indeed discover that St. Thomas can play the role of the true teacher in guiding us to the truth.




Works Cited

Adler, Mortimer. The Difference of Man and the Difference it Makes. New York: Holt, Rinehart and Winston, 1967.

Clarke, W. Norris. One and the Many: A Contemporary Thomistic Metaphysics. Notre Dame: University of Notre Dame Press, 2001.

Collins, Francis. The Language of God. New York: Simon and Schuster, 2006.

Dawkins, Richard. The God Delusion. New York: Houghton Mifflin, 2006 .

Fathers of the English Dominican Province. Summa Theologica of St. Thomas Aquinas. 1920.

Pope John Paul II. Discourse to the Academy of Sciences. Vatican City, 1996.

“Message to the Pontifical Academy of Sciences: On Evolution.” EWTN. October 22, 1996. (accessed December 6, 2011).

Maritain, Jacques. “God and Science.” EWTN. 1965. (accessed December 6, 2011).

Pieper, Josef. The Silence of St. Thomas. New York: Pantheon Books, 1957.

Schonborn, Christoph Cardinal. Chance or Purpose. San Francisco: Ignatius Press, 2007.

  1. John Paul II, Message to the Pontifical Academy of Sciences on Evolution, 5.
  2. John Paul II, Message to the Pontifical Academy of Sciences on Evolution, 4.
  3. John Paul II, Discourse to the Academy of Sciences, 1.
  4. John Paul II, Message to the Pontifical Academy of Sciences on Evolution, 4.
  5. Summa Theologiae (ST), I, q.32, a.1.
  6. ST, I, q.47 a.1.
  7. ST I, q.5, a.3.
  8. ST I, q.25, a.6, ad.1.
  9. Cardinal Chrisoph Schonborn, Chance or Purpose, pp.97-98.
  10. W. Norris Clarke, One and the Many¸ pp. 150-153.
  11. Ibid., pp.109-123.
  12.  Jacques Maritain, “God and Science”
  13. Schonborn. Chance or Purpose, p.99.
  14. C.f. Richard Dawkins, The God Delusion,  pp.100-101.
  15. ST I, q.2, a.3.
  16. ST I, q.22, a.4.
  17. W. Norris Clarke, One and the Many, p.247.
  18. ST I, q.78, a.1.
  19. W. Norris Clarke, One and the Many, p.251.
  20. Mortimer Adler, The Difference of Man and the Difference it Makes, p.94.
  21. C.f. Francis Collins, The Language of God.
  22. W. Norris Clarke, One and the Many, pp. 255-56.
  23. For a full synthesis of Thomism and modern science in relation to the difference of man, see Adler’s book.
  24. Josef Pieper, The Silence of St. Thomas, pp. 107.
Rob Agnelli About Rob Agnelli

Rob Agnelli holds an M.A. in moral theology from Holy Apostles College and Seminary. He lives in Raleigh, North Carolina with his wife, Allison, and their three sons. Rob teaches bioethics throughout the Diocese of Raleigh, and is part of a national speakers' panel in which he addresses issues related to marriage, fatherhood, and moral theology. He has published numerous articles related to the Catholic faith in journals such as the National Catholic Bioethics Center's Ethics and Medics newsletter, Homiletic and Pastoral Review magazine, and Social Justice Review.