Encyclopedia of Teacher Education

Living Edition
| Editors: Michael A. Peters

Aquinas as a Guide for Teaching Philosophy

  • Curtis L. HancockEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-981-13-1179-6_148-1


Arguably, the best way to learn philosophy is to examine it in the laboratory of history. The limitation of this method is a tendency to reduce past philosophers and their ideas to a catalogue of museum pieces. Such a limitation can be overcome provided one remembers that the judgments of philosophers, in the last analysis, ought to be tested for their truth content. This regard for the pursuit of truth is enhanced by examining philosophical arguments in their historical context, which reminds one that historically philosophy develops as something organic and reactive. Philosophical change happens, even schools of thought come and go, because they are tested in the crucible of history. Samuel Johnson called the history of philosophy “the great conversation,” a description that captures the dialogical nature of the discipline.

Subsequent generations contemplate what their predecessors have said and often consider how they must disagree with them. On the other hand, successive generations might renew their regard for their ancestors, perhaps discovering (or recovering) truths forgotten or overlooked. For these reasons, investigating the history of philosophy can occasion humility, as one discovers that philosophies supposedly long dead are still relevant.

There are important voices still pertinent from the history of philosophy. Thomas Aquinas stands out because he is an unambiguous dialectical counterpoint to modern philosophy. His thought is a crystallization and representation of the best of classical philosophy, the elements of which are, as a rule, different in kind from the assumptions of modern thought. This makes his philosophy especially serviceable in the classroom. Students seldom witness the accepted views of modernist philosophers challenged on a substantive level. This is not surprising, since for generations philosophical problems have been determined by assumptions emanating out of Renaissance and Enlightenment thinkers, such as Bacon, Hobbes, Descartes, Hume, and Kant. Even subsequent thinkers who disagree with these modernists nonetheless tend to accept their basic assumptions. If an instructor aims to provide a Socratic analysis and investigation of modern and contemporary ideas, Aquinas can be immensely helpful.

One way he is helpful is to challenge a presumptive atheism that sometimes surfaces in today’s classrooms. Often this atheism emerges through the influence of the “New Atheists,” like Richard Dawkins and David Barash (Dawkins 2006; Barash 2018), who hold that an enlightened mind reduces knowledge to physical science and that physical science justifies atheism. Of course, the inference that science implies atheism is fallacious. And yet, in both academic and popular culture, such an inference has become fashionable. Aquinas is an effective counterpoint to this presumptive atheism.

Since many scientists, past and present, are theists, it is dogmatic to conflate science and atheism. It is noteworthy that this conflation is not really a scientific position. Instead, it is a philosophical conception of science called scientism, a conception containing many beliefs, one of which is atheism. In other words, scientism is a worldview, a comprehensive claim to wisdom consisting of the most fundamental beliefs, convictions involving reality, knowledge, human nature, morality, and politics. By applying Aquinas’s philosophy critically to scientism, an instructor can demonstrate Aquinas’s continuing relevance by using his wisdom to address fundamental inquiries in the philosophical classroom.

To put scientism in perspective, the work of Mikael Stenmark is instructive (Stenmark 2001). He summarizes scientism in terms of the following adjectives: ontological, epistemic, axiological, and existential scientism. By observing Stenmark’s outline, an instructor can address an atheist’s entire worldview and show its limitations. Aquinas, because of the power of his comprehensive philosophy, can show students why atheism is problematic and why scientism is fallacious.

Ontological scientism asserts “the only reality that exists is the one science has access to.” Carl Sagan’s opening remark in his program Cosmos expresses this kind of scientism: “the cosmos is all that is or ever was or ever will be.” Epistemic scientism maintains that “the only reality that we can know anything about is the one science has access to.” When scientists assert that our knowledge is limited to what empirical science can quantify, they are asserting epistemic scientism. Stenmark adds axiological scientism: “science alone can explain morality and replace traditional ethics.” Behavioral and evolutionary scientists often advance this kind of scientism. Lastly, Stenmark specifies existential scientism: “the idea of salvation through science alone,” the view that “science alone can explain and replace religion.”

With these clarifications in place, one can exercise Aquinas’s dialectical power to show students that scientism is objectionable. This application of Aquinas to scientism illustrates how Aquinas is a guide for teaching philosophy in a plurality of analogous ways, from metaphysics to ethics.

Ontological Scientism

Philosophers often assert scientism on the most fundamental level when they presume physical monism, sometimes called materialism, or philosophical naturalism. These expressions alternatively signify that the only thing that exists is matter. Associated with this materialism is invariably mechanism, the view that the universe is purposeless and that material and efficient causes suffice to explain the structure and behavior of the universe.

An instructor trained in the work of Aquinas can readily expose that the materialist-mechanistic worldview is unconvincing. Aquinas can show this through the demonstration of God’s existence. If God exists, materialism is falsified. God cannot be God, Aquinas argues, unless God is incorporeal. Theism is instructive in two ways: (1) by showing students that demonstrating God’s existence is possible, despite the cavalier dismissal of theism in today’s intellectual culture, and (2) by refuting not only materialism but also mechanism, this last accomplished by defending Aquinas’s fifth way.

The first task, demonstrating God’s existence, becomes possible by explaining that David Hume’s account of causality (something of an idol of the intellectual tribe) is unconvincing. Once the metaphysician can show that it would be unreasonable to doubt the necessity of the causal relationship, theism becomes defensible. So, without wading into the details of Aquinas’s five ways, one can show how an effective groundwork for them can be established by relying on Aquinas to escape Hume’s explanation of causality. Aquinas’s proofs for the existence of God rely on causality. Students can witness an instructor effectively refute atheism by first rescuing causality from Hume’s skepticism.

Aquinas can reveal two arbitrary assumptions in Hume’s conception of causality. Once these assumptions are exposed, the student can see that a philosopher has a right to revisit theism in a constructive way, unencumbered by Hume’s doubt about causality. Hume’s two assumptions are (1) that the relation of cause and effect is one of temporal succession and (2) that, since these temporal events are distinct, one can imagine that one could occur without the other. In response to these assumptions, Hume concludes that belief in causal necessity is just an expectation, a habit of mind conjured by the experience of constant conjunction between certain events.

Aquinas, like Aristotle, would strongly object to Hume’s reduction of causality to a temporal relation. Accepting Hume’s interpretation prejudices the case that effect is not necessarily related to cause. Since the mind can conceptually distinguish what comes before from what comes after, and since, Hume believes, what is conceptually distinguishable is in fact separable, it follows that an effect (what comes after) is not necessitated by a cause (what comes before). Aquinas would object that Hume’s analysis is fallacious and bizarre.

As Edward Feser has explained, Aquinas understands that the causal relation is not between events but things (Feser 2009). Once one overcomes Hume’s reduction of causality to a temporal relation, one can escape his skepticism and restore metaphysics. Aquinas would correct Hume by pointing out that causality is a relationship of simultaneity, not of succession. This simultaneity indicates dependency of one thing on another. Hume fails to grasp the nature of causal dependency by overlooking the primacy of simultaneous relatedness in the tandem of cause and effect.

Hume thinks that when a burglar throws a stone through a window, the causal event involves a discrete temporal moment being followed by another discrete temporal event. According to Aquinas, this conception of causality is a mistake. It is the simultaneous combination of the stone and the shattering glass that is the causal relationship. That the stone exists before the glass is irrelevant to the causal relationship. Central to causation is that the cause exists at the same time as its action on the effect. Once the causal occurrence is seen in this light, it is unreasonable to think cause and effect are separable and unrelated necessarily.

Aquinas’s correction undercuts many of the bold and strange outcomes Hume, and his followers claim about causation. Hume thinks that because cause and effect are conceptually separable, anything whatsoever could follow from any cause. If the relationship is not necessary, why couldn’t something become without a cause? Why couldn’t something just “pop into existence”? This possibility is supposed to nullify metaphysics once and for all. However, once edified by Aquinas, one is under no obligation to play Hume’s conceptual game on his rules. One has a right to reassert a commonsense belief in the necessity of cause-and-effect relations.

This use of Aquinas in the classroom has profound implications. It restores metaphysics by vindicating the demonstrability of theism. On a posteriori grounds, the philosopher can endeavor to persuade students that God exists. God is the necessary cause of the universe. Each of the five ways emphasizes this conclusion relying on different causal perspectives. The fifth way, Aquinas’s version of the design (or teleological) argument, is telling because it refutes mechanism.

When the typical atheist undergraduate is referred to Aquinas’s fifth way, she or he will equate it with William Paley’s so-called Argument from Design, according to which the universe must have a designer because it is a mechanism (analogous to a machine, like a watch) and it is unreasonable to doubt whether mechanisms have designers. Paley is the New Atheists’ obligatory whipping boy, and the student is likely to dutifully accept their refutation of his Argument from Design. Atheists respond to Paley because his argument from design is an available straw man. Paley’s argument is flimsy because it accepts materialism and mechanism as its starting point, contending that while the physical universe consists only of material and efficient causes, it nonetheless points to a divine designer because of its (perhaps irreducible) complexity.

This argument is weak compared to Aquinas’s fifth way, which maintains that teleology is immanent to the universe, not something added by an external efficient cause or designer. Substances in the universe behave purposively, according to Aquinas, because of their natures, which fulfill themselves by their activities. Richard Swinburne (1968) has resurrected this argument, insisting that it is much stronger than Paley’s because it appeals to the behavior of things rather than their mere appearances (however complex). The New Atheists seem unaware of any of this, apparently taking Paley’s proof as the theistic argument of choice, the best the tradition presumably can muster. Students benefit from being shown the contrast between Paley’s Argument from Design and Aquinas’s fifth way.

The fifth way is especially effective at addressing the New Atheists’ strategy to substitute Darwinian evolution for God. Aquinas would be bemused by this use of evolution to scientifically explain how the universe lacks fundamental intelligible principles that would make science possible in the first place. Aquinas lived 600 years before Darwin, but he was familiar with the idea of evolution generally. Saint Augustine had presented a doctrine about evolution 800 years before Aquinas’s birth. Aquinas would know that evolution, whether cosmic or biological, cannot be grounds to justify atheism.

The New Atheists, presumably following Darwin, argue that the matter of the universe is fundamentally disordered and yet by chance, an apparent order evolves out of it. Aquinas would challenge this view of the universe. Were Aquinas familiar with the details of Darwinian evolution, he would conclude that evolution is not evidence against God because (1) evolution rests on the existence of things, which requires a Creator God, and (2) evolution requires underlying scientific laws. These laws are an underlying order governing all other behavior of matter. Evolutionary biologists are either misinformed or disingenuous when professing that the processes of nature manifest an order emerging out of an underlying disorder. To the contrary, evolution represents an order coming forth from a previous order.

Epistemic Scientism

It is worth noting that epistemic scientism does not necessarily commit one to ontological scientism. One could hold that knowledge happens to be limited to physical science without ruling out the possibility that God or other nonphysical beings exist. But the typical undergraduate atheist, under the influence of the New Atheists, embraces both ontological and epistemic scientism, because atheism commits him or her to materialist-mechanism and, accordingly, there is nothing that can be known that is not physical.

Aquinas would say that the philosopher should know better than to accept these limitations. There are entire orders of knowledge that transcend matter. Objects of knowledge include theology, metaphysics, and moral truths. None of these is an object of physical science. Aquinas would insist that truth itself is not something that physical science can explain. Science is about knowledge, and knowledge is another word for truth. So, Aquinas would challenge whether a worldview committed to physical monism (materialism) could explain the nature of truth.

Truth is an operation of the intelligence, and a physicalist paradigm cannot explain that operation. One must ask how the human mind grasps truth, judgments about what is or is not the case. How truth is generated is an intractable problem for physical monism. If everything has a physical nature only, the activity of knowledge has a physical explanation. According to physicalists, knowledge takes place through brain activity, electrical and biochemical behavior in the central nervous system. Philosophical naturalists and many scientists assert this explanation of knowledge, or truth, as obvious. But Aquinas would reject it as farfetched. First, truth is a reflexive awareness of what is or is not. In truth one not only knows but knows that one knows (at least implicitly). How is this reflexivity of awareness possible if the human mind is just brain or neurological activity? Secondly, the mind somehow must extract information from the external world and appropriate it. This means that in truth about real things, there is a kind of abstraction, from the Latin ab-trahere, to draw out of. In other words, the knower must dematerialize what is known so that it assimilates into human consciousness, because the object known exists in cognition without physical parts.

Aquinas would resist calling the examination of knowledge epistemology. He would insist that it is better named the metaphysics of knowledge because truth transcends physics. Knowledge may start in sensation, but the abstract power and judgment of the intelligence make the attainment of truth a metaphysical act. This analysis of knowledge, Aquinas would point out, makes the pursuit of knowledge for scientism something of an embarrassment. On the basis of physical monism, there can be no science. And yet science is the raison d’etre for scientism. If materialism cannot explain knowledge, there is no science, nor scientism.

Axiological Scientism

Aquinas would additionally object to the use of evolutionary biology to explain morality, an explanation that is fashionable. Evolution is invoked to provide a scientific basis for our desire to be moral, which evolutionists understand as our disposition to get along with others. Evolutionists, like Dawkins and Barash, argue that morality evolved because cooperation was adaptive. Natural selection determined the genetic transmission of cooperative tendencies to insure the survival of individual and tribe.

Aquinas would not be loath to accept evolution as part of the story of human behavior and survival, provided it coheres with teleology. But evolution will not suffice to explain morality because morality is more than just “getting along.” Morality involves relating to others according to standards about what is right, and adaptation alone does not capture what is right. Hypothetically, cruelty could be adaptive, but it is not right. Evolution’s interpretation of human nature is narrow and anemic, unable to explain morality in a comprehensive way. Aquinas argues that a sound morality requires an appreciation of the human person as a creature with free will. How can free will be accounted for in the Darwinist’s materialist reductionism? Besides, Aquinas would add, morality loses depth when it is divorced from religion. If one sees another as the image of God, one is inspired to relate to that person in a deeper way than if one sees another as a product of pointless evolution.

Existential Scientism

If atheists are consistent, they must deny that there is purposiveness in the universe. If there are only material and efficient causes – that is to say, if there are no natures (formal causes) directing themselves toward fulfillment (final causes), not to mention no divine intelligence influencing nature – then the universe is essentially purposeless. The universe is purposeless and human beings must live with that fact. To their credit, atheists usually own up to this consequence of scientism.

Still, this admission does not immunize the atheists from criticism. Aquinas would insist that the universe makes sense because things have natures and behave in specific ways to actualize those natures. Contrary to what the New Atheists might say, modern science has done nothing but support Aquinas’ teleological outlook. The universe abounds with specific behaviors that show purposiveness. Flammable things ignite; they don’t generate ice. The rock cycle operates through specific and predictable stages. Likewise, the water cycle is an object of science because it regularly proceeds from collection to evaporation to condensation to precipitation and back to collection. The organs of animals are species-specific in their actions. Hearts have their function and they do not do what kidneys do. Each contributes to the life processes of the organism. The universe abounds with such examples.

Aquinas’s science might have been medieval, but there is nothing in modern science that undercuts his Aristotelian teleological outlook. Aquinas would be delighted to learn about DNA and he would say that it vindicates teleology in biology. He would concur with Max Delbrück, an erstwhile Nobel laureate in physics, who declared that “they should consider Aristotle for the discovery of the principle implied in DNA.” But “the reason for the lack of appreciation, among scientists, of Aristotle’s scheme lies in our having been blinded for 300 years by the Newtonian view of the world” (Feser 2009).

Furthermore, Aquinas would highlight the commonsense evidence that human beings do not live satisfying lives without a sense of purpose. Whence derives this sense of purpose, if, for the evolutionist, the universe is purposeless? Aren’t the champions of scientism a peculiar breed if they devote their lives, through research and polemics, to proving that the universe has no purpose? Aquinas would echo Whitehead’s bemused observation that “those who devote themselves to the purpose of proving that there is no purpose constitute an interesting subject for study” (Feser 2008).


Since scientism consists of a worldview that is likely to emerge in today’s philosophical classroom, it is instructive to outline how it can be assessed. The philosophy of Saint Thomas Aquinas offers considerable resources to make this assessment. Since scientism forces the philosopher to confront fundamental principles and beliefs, and since such fundamentals apply to standard philosophical classroom subjects and issues, Aquinas’s ability to confront, clarify, and evaluate such matters indicates how he can be an invaluable guide for teaching philosophy.



  1. Barash, D. (2018). Through a glass brightly: Using science to see our species as we really are. New York: Oxford University Press.Google Scholar
  2. Dawkins, R. (2006). The god delusion. New York: Houghton-Mifflin.Google Scholar
  3. Feser, E. (2008). The last superstition: A refutation of the new atheism. South Bend: St. Augustine’s.Google Scholar
  4. Feser, E. (2009). Aquinas: A beginner’s guide. London: Oneworld.Google Scholar
  5. Stenmark, M. (2001). Scientism: Science, ethics, and religion (pp. 1–17). Aldershort: Ashgate.Google Scholar
  6. Swinburne, R. (1968). The argument from design philosophy. 43, 199–212.CrossRefGoogle Scholar

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© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  1. 1.Rockhurst UniversityKansas CityUSA

Section editors and affiliations

  • Janis (John) Ozolins
    • 1
  1. 1.School of PhilosophyAustralian Catholic UniversityMelbourneAustralia