Thomism and Evolution

I’m sharing the good news. My article on the thomistic response to the theory of evolution – that I have been working on for a long time – has been published today in an online version of the coming issue of Theology and Science. you can find link to the article and a pdf of the final draft on my profile on ACADEMIA.EDU and RESEARCHGATE.NET.

The paper is significant for two reasons.

First, I’m bringing in it my discovery of a preliminary definition of natural selection in Aquinas’ commentary on Aristotle’s Physics II, 8 (198b 29-32), that can be found in In Phys. II, lect. 12, par. 253.

Second, in the theological part of the paper I bring Aquinas’ Commentary on Sentences (In I Sent., dist. 44, I, 2, co.) where Thomas — in the context of divine action in the possible perfection of the universe — says explicitly about addition of new species (multae aliae species).

Thomistic Response to the Theory of Evolution: Aquinas on Natural Selection and the Perfection of the Universe


Neither Aristotle nor Aquinas assumes the reality of the evolution of species. Their systems of thought, however, remain open to the new data, offering an essential contribution to the ongoing debate between scientific, philosophical, and theological aspects of the theory of evolution. After discussing some key issues of substance metaphysics in its encounter with the theory of evolution (hylomorphism, transformism of species, teleology, chance, the principle of proportionate causation), I present a Thomistic response to its major hypotheses. Concerning the philosophy of Aquinas I trace what might be seen as a preliminary description of natural selection in his commentary on Aristotle’s Physics. Turning toward theology, besides addressing the topics that were referred to in the past—such as: Aquinas’ reading of Genesis, his account of creation as dependence in being, secondary and instrumental causality, and univocal/equivocal predication of God—I bring into discussion Thomas’ concept of the perfection of the universe, which has been virtually unused in this context.

Key Words: Aristotle; Aquinas; Natural selection; Chance; Divine causality; Evolution; Hylomorphism; Perfection of the Universe; Teleology

Aristotle & Evolution

I want to share the news about my latest publication – an article on Aristotle and evolution published in the proceedings of the 1st Virtual international Conference on the Dialogue between Science and Theology organized by RCDST of Ovidius University of Constanta, Romania.

An Aristotelian Account of Evolution and the Contemporary Philosophy of Biology

The article is also available HERE

Proceedings of the conference



The anti-reductionist character of the recent philosophy of biology and the dynamic development of the science of emergent properties prove that the time is ripe to reintroduce the thought of Aristotle, the first advocate of a “top-down” approach in life-sciences, back into the science/philosophy debate. His philosophy of nature provides profound insights particularly in the context of the contemporary science of evolution, which is still struggling with the questions of form (species), teleology, and the role of chance in evolutionary processes. However, although Aristotle is referenced in the evolutionary debate, a thorough analysis of his theory of hylomorphism and the classical principle of causality which he proposes is still needed in this exchange. Such is the main concern of the first part of the present article which shows Aristotle’s metaphysics of substance as an open system, ready to incorporate new hypothesis of modern and contemporary science. The second part begins with the historical exploration of the trajectory from Darwin to Darwinism regarded as a metaphysical position. This exploration leads to an inquiry into the central topics of the present debate in the philosophy of evolutionary biology. It shows that Aristotle’s understanding of species, teleology, and chance – in the context of his fourfold notion of causality – has a considerable explanatory power which may enhance our understanding of the nature of evolutionary processes. This fact may inspire, in turn, a retrieval of the classical theology of divine action, based on Aristotelian metaphysics, in the science/theology dialogue. The aim of the present article is to prepare a philosophical ground for such project.

Philosophy of Causation – Vol. 1 – Ancient Greece

I have recently accomplished my Special Comprehensive Exam which is a major step on the way of my doctoral studies at the GTU in Berkeley, CA. The first part of the project was a written exam which covered some of the major developments of the theory of causation in ancient, medieval, and modern philosophy. In this post I publish the first part of the exam, the one referring to the ancient tradition. I hope the readers of my blog will find it interesting. Remaining parts are to come soon.


The development of the reflection on causality in ancient Greece has its beginnings in the philosophy of early Milesians, who presented three positions on the problem of change in nature. According to the first and predominant option some things change (totally or in some ways), while other things do not go through the process of change. Noticing this, some of the philosophers looked for a fundamental principle which does not change and remains constant. Thus, we can say that they gave the origin to the reflection on material cause. Thales (620-550 BC) claims that the fundamental constituent which remains unchanged is H2O. It can exist as solid, liquid or vapor. Hence, all things are water in various states. Anaximenes (570-500 BC) takes air for the basic stuff and says that everything is really air in different forms of rarity or density. Anaximander (610-525 BC) takes an important step saying that none of the basic elements (earth, fire, water) can be the first principle for it would destroy other elements. He enters a meta-level of philosophical reflection saying that the undetermined principle is most fundamental and may be called “the infinite.” It is by joining and separating of opposite qualities present in “the infinite” that all things come into being and change. (Michael Dodds rightly says that if we substitute “energy” for “air,” Anaximenes becomes Einstein. Heisenberg saw Anaximander’s “infinite” equivalent to “energy” in modern physics. Dodds argues that his description is closer to Thales: instead of H2O we have “matter” or “energy.”)


The second view of change among early Greek philosophers is represented by Heraclitus (fl. 500 BC) and assumes that all things are constantly changing. Things are just ephemeral patterns of continuity in the perpetual flux of the world. (Dodds finds this position similar to the contemporary philosophy of process). The third view represented by Parmenides (fl. 500 BC) remains in opposition to the former one, as it assumes that nothing really changes in nature. Things either “are” or “are not,” there is no other option, and thus nothing can change. For a new thing could come into being only from non-being (which is impossible), or from being (which would mean that it existed before). Therefore, change is an illusion.

The conceptual level of Anaximander’s reflection (as distinct from more empirically grounded philosophy of other Milesians) finds its continuation in Anaxagoras (c. 510-428 BC), who declares cosmic intelligence (mind, nous) to be what causes everything. But since intelligence seeks what it values, this kind of explanation exceeds an interest in material cause, predominant among Anaxagoras’ predecessors, entering the new level of explanation, which is teleological in style. Hence, we can find here the first primitive notion of final causation. However, Plato (Socrates in Phaedo) claims that the details of Anaxagoras’ reflection show that he was not aware of this commitment (he concentrates mainly on materialistic factors such as air, water, and vortex).

The further step on the way of defining causality was taken by Empedocles (ca. 495-435 BC) who presents the first reflection on efficient cause. He claims that besides the elements of earth, air, fire, and water, two further elements, “love” and “strife” are needed in order to combine or keep apart the basic elements. The idea of efficient cause was developed later on by Democritus (ca. 460 – ca. 370 BC) and atomists, who would remain in opposition to the idea of final cause of the universe, arguing in favor of the purely mechanical view of causation (movement and collisions of atoms).


Among the earliest philosophical schools we find one more which remains at odds with those described so far. It is the school of Pythagoras (ca. 570- ca. 490 BC), who was the first to make an attempt to understand the cosmos and its phenomena in terms of number. His reflection was rooted in Egyptian geometry and Babylonian arithmetic. Pythagoras used them to develop a philosophy of nature based on mathematics. He suggested a parallelism between the idealizations of geometry and the physical patterns of the universe. According to him, number underlines all physical objects and its study reveals deeper level of reality than is apparent on the surface. Aristotle would say, later on, that Pythagoreans considered number to be the principle of both matter (even or “unlimited” elements of number) and form (uneven or “limited” elements of number). Thus, every physical entity is explainable in terms of mathematics. From this basic point the Pythagoreans went to a detailed study of mathematical proportions, harmonic relationships, and irrational numbers, which gave the origins to a study of continuum and infinite divisibility.

Penrose tiles

Pythagorean ideas combined with Democritus’ atomism inspired Plato (428/427 or 424/423 – 348/347 BC) to present his geometric theory of matter. The originality of his theory is based on the fact that he regards matter (“the mother of all becoming”) as a stable and eternal receptacle for Ideas of Forms, and thus formulates the first notion of formal causation. He is also probably the first one to state explicitly the principle of causality in Timaeus: “everything that becomes or changes must do so owing to some cause; for nothing can come to be without a cause.” For Plato the world accessible to our sensual experience is changing and made of appearances. It is merely a shadow of the true reality which is the world of autonomous and immaterial Forms. If the formless matter is “the mother,” the eternal form is “the father,” and the transitory phenomena known to our senses are their offspring. The elements of the physical world are construed on the model of geometrical patterns: fire takes the shape of tetrahedron, air of octahedron, and water of icosahedron. All of these shapes are made of multiplied triangles. Therefore, the triangle can be regarded as an atomic element in Democritean sense.

What remains crucial for our further reflection is the fact that neither Pythagoras nor Plato regarded mathematics, as did Aristotle, as a formal and abstract discipline which applied to reality enables us to construe a subalternated type of scientific knowing, abstracted from empirical and sensual experience. They saw it rather as a way of arriving at the ultimate and basic reality itself, which in sensual experience is given only in ephemeral appearances.


Aristotle (384-322 BC) presents the most developed theory of causation among philosophers in ancient Greece. He systematizes and further develops the teaching of his predecessors, defining four kinds of causality in Posterior Analytics, Physics, and Metaphysics (he alludes to various causes in other works as well). Material cause for Aristotle means not only the basic building stuff. He introduces the term of primary matter (prōtē hulē) which he understands as a principle of potentiality, something that persists through all changes that a given substance can be exposed to (something that constitutes the very possibility of being a substance at all). Concerning formal cause, Aristotle remains in a radical opposition to the transcendental character of Ideas in Plato. For him forms must be in things, determining their actuality. Formal cause answers the question “why” something is the kind of a thing it is, and it cannot be reduced to “shape” or “appearance” of a thing. Aristotle introduces also an important distinction between accidental and substantial form, which he explains in terms of changes that effect in an “alteration” (an accidental change), which does not change the substantial principle of a substance, as opposed to a situation in which the thing changes as a whole (coming-to-be of a new substance). For Aristotle material and formal types of causation are intrinsically related. They can be separated only in mental reflection. In reality we know primary matter only as informed, and form only as informing primary matter.

The other two causes indispensable for Aristotle’s description of reality are: efficient and final. The former one is generally defined as an activity of an agent bringing motion or rest. However, Aristotle classifies as efficient causality also activities such as giving an advice, which in some of its aspects goes beyond physical interaction and exchange of energy. The latter, final cause, he defines as “that for the sake of which” a thing is done, or a good proper for a thing that can be attained. It is important for him to notice that final causality should not be associated merely with conscious and rational human decisions. He speaks about natural teleology which is present both in inanimate and animate nature even if it “does not deliberate.” Finally, Aristotle emphasizes the relation between efficient, formal, and final causation, noticing at the same time that final cause is the first and should be regarded as causa causarum.


Aristotle devotes no less than three chapters of the second book of Physics to the study of chance and necessity. He criticizes philosophers of the past for either not finding a place for chance on their list of causes, or not paying enough attention to it. He refers specifically to Empedocles who attributed to chance certain events, such as movement of air in the process of the separation of elements, or the origin of the parts of animals, but did not analyze the nature of chance in more detail. He is also critical about Democritus who attributed the origin of the universe to spontaneity, claiming at the same time that chance is not responsible for the generation of plants, animals, or mind. Such an explanation ascribes the causes of things to both necessity and chance, understood as the “absence of purpose.” Following this line of thinking, Plato (Timaeus) saw both necessity and chance as inherent in the material cause, which is formed by the Demiurge (reason) who strives to prevail over necessity of matter resistant to order. Because the reason cannot succeed fully in its endeavor, chance events occur which show no order.

Contrary to Empedocles, Democritus, and Plato, Aristotle claims that necessity, which implies order, is irreconcilable with chance, which occurs contrary to a given order. Thus, Aristotle distinguishes chance events from occurrences that happen necessarily, and those happening in the same way for the most part. Chance events also have a unique character in his second classification, in which Aristotle distinguishes between events that come to be for a purpose (due to a deliberate intention or as a result of nature), and those that do not happen for a purpose. He says that “even among the things which are outside the necessary and the normal, there are some in connection with which the phrase ‘for the sake of something’ is applicable. (…) Things of this kind, then, when they come to pass incidentally are said to be ‘by chance’.” In reference to his distinction between per se and per accidens causality Aristotle states that chance is an unusual accidental cause, and as such it is inherently unpredictable, although it still falls in the category of events that “happen for the sake of something.” Although chance events are due to nothing in the substance or per se cause which happens to concur with these unexpected occurrences, as an accidental cause, chance occurs always and only in reference to per se causes. Therefore, chance occurrences for Aristotle are always posterior and inherently related to nature (φύσις) and intellect (νοῦς). Hence, they are associated with formal and final causality rather than material necessity.


The ancient philosophical reflection on causality notes one last important contribution brought by Stoicism (3rd cen. BC), which would have a major influence on the development of modern accounts of causation. Stoics linked causality with exceptionless regularity and necessity. We can list five of their most basic theses concerning causation: 1) Cosmos is an organism imbued with divine reason (logos) and ordained by fate; 2) Nothing happens without a cause; 3) Causation involves exceptionless regularity; 4) All particular events necessitate their effects; 5) There is a fundamental distinction between external and internal causes. The last rule seems to be an answer to a controversy concerning human freedom which appears to be undermined in Stoicism (Cicero, De fato). An external cause is only auxiliary and proximate while an internal cause is called principal and perfect. Every human action is a response (based on internal cause) to an external cause producing sense-impressions. The consistency of this theory is questionable, and the action of human being in Stoicism seems to depend entirely on determinism of nature and fate.

Summing up, we can see that the ancient tradition offers a variety of approaches to the problem of causation. It developed a fourfold division of causes defined by Aristotle which will prove to have a substantial influence on medieval philosophy of nature and its steps towards understanding of the world and its processes, opening the way to natural science of modernity.