Thomism 101: My Philosophical Commitments, Briefly Explained

I identify as a Thomist—by which I mean I believe Thomas Aquinas was generally right on the most significant philosophical questions and how he addressed them.

I identify as a Thomist—by which I mean I believe Thomas Aquinas was generally right on the most significant philosophical questions and how he addressed them.

I thought it might be useful, in this article, to briefly list (not defend) what these positions are, so it’s clear what my Thomism actually entails and, just as importantly, what it doesn’t.

Let me begin by saying I see Thomas not so much as one of the first great medieval philosophers, but rather perhaps the last great classical philosopher. To me, Aquinas is the thinker who brings the whole tradition—what Lloyd Gerson calls Big Tent Platonism—to its perfection and completion.¹ He is, of course, well known for his ability to synthesize Aristotelian and Neo-Platonic schools, but he was also highly original; he wasn’t merely a synthesizer but, in many important respects, a philosophical pioneer—especially concerning his theory of existence.

Still, I want to emphasize that by identifying as a Thomist, I am, by default, identifying as a Big Tent Platonist. This means I am committed to classical philosophy and see myself as a classical philosopher.² So the question becomes: what is classical philosophy, and what are the positions held by the classical philosopher I most identify with—Thomas Aquinas?³ These positions—some, but not all—are as follows:

• Philosophy as a distinct discipline: Philosophy is a distinct discipline where distinctly philosophical truths can be discovered (it’s not just conceptual cleanup for science). Moreover, there is a correct philosophical system, and the ultimate aim of philosophy is not just to uncover individual truths but to adopt the correct system—a systematic and articulated vision of the whole.

• Metaphysical realism: There is a world beyond our minds that exhibits many features independent of mind and language.

• Essence realism: Classical philosophy denies nominalism, understood as the view that there is no conceptual space for sameness apart from strict identity. Real sameness exists and is accounted for by shared (though numerically distinct) essences, such as human essence or tree essence.

• Abstract objects: Thomists affirm the reality of universals but only as immanent in particulars or abstracted by the mind. There is no Platonic heaven or independent realm of existing abstracta.

• Transcendentals: Every being is one, active, true (intelligible), and good. These properties apply to everything insofar as it exists and are identical with the being itself, rather than something added onto it.

• Analogy & Modes of Being: Being is expressed in many ways—there are different modes of existence. Some things exist in a substantial or fundamental way, while others exist in a derivative or accidental way. Related to this is the tool of analogy, or the use of "stretch concepts" (similarity within difference), which is essential for making sense of the world with its various modes of being. Analogical predication becomes especially important in the philosophy of God to avoid anthropomorphism or absurdity when discussing divine attributes. When we attribute qualities like power, knowledge, or goodness to God, it’s crucial to understand that these are predicated of God in a way entirely different from how they are predicated of us. God's attributes exist in a mode that is infinitely higher and more perfect than our own.

• Moral realism: There are stance-independent moral truths, rooted in perfectionism and the convertibility of being and goodness. Classical moral realism stems from real essentialism, particularly essences and natural teleology. Things have a nature, and that nature is oriented toward a particular end—its flourishing. For humans, flourishing means knowing and loving what is ultimately most true and good: God. Moral knowledge is possible for humans, and Thomists are non-consequentialists, committed to a broad virtue ethic and a natural law account of the good life.

• Reality as completely intelligible: Thomists hold that there is an adequate answer to every coherent question about reality, though this doesn’t mean that finite beings like us can fully grasp everything; perhaps only God can. Thomists accept a version of the principle of sufficient reason and reject the notion of brute facts.

• Fundamentality of substances: Substances are the primary existents—familiar medium-sized objects like people, trees, etc. A substance is whatever exists in itself (and not in something else, like a lump exists in a rug). Everything that isn’t a substance is an accident (e.g., quantity, quality, relation). Moreover, substances are unified, organized centers of activity, with parts that depend on the whole, as the parts are integrated toward the good of the whole and are known only in relation to the whole.

• Constituent ontology: Most things have parts—not just physical parts but also metaphysical parts, or constitutive principles, from which they derive their character. Following Aristotle, Aquinas holds that every material substance is a composite of form (the principle of organization) and matter (the principle of individuation)—this is hylomorphism. A tree is what it is because of its form, and it is this particular tree because of its matter. Constituent ontology is also necessary to account for change: for something to change, something must remain the same. This is where “parts” play a crucial role: if a thing is composite, it can remain what it is essentially while gaining or losing something non-essential. This allows for the preservation of diachronic identity while affirming the reality of change. For example, standing Socrates is the same as sitting Socrates because he has substantial unity (the same substance in different configurations), yet different because something is gained or lost—a metaphysical accident (standing-ness, sitting-ness, etc.). For Aquinas, different types of composition (substance-accident, form-matter, essence-existence) within familiar objects all relate as potency to act.

• Act & Potency: Aristotle’s act-potency distinction, which Aquinas accepts and ingeniously applies, allows us to hold onto the reality of change and permanence, parts and wholes, while avoiding paradoxes. Simply put, “Act = the actuality or presence of some positive mode of perfection. Potency = the potential subject that receives and limits act, and is the principle of continuity underlying and determining the limits of the actual changes it can undergo.”

• Existence is a REAL property: Existence is something that things actually have—or more accurately, participate in. It is what makes something a real being, giving it actual presence in the world and making it capable of influencing and being influenced. For everything apart from God (whose essence is existence), beings are composites of an essence element—a what-ness determination—and an existence element—an is-ness determination. Importantly, existence isn’t like other properties; it’s not something that inheres in an already existing subject (which would be absurd). Rather, it is what makes the entire subject (and its properties) actually exist.

• The existence of God: for the Thomist, God is understood as a being whose essence is existence itself—purely actual, immutable, eternal, omnipotent, omniscient, and perfectly good. God is the ultimate source of existence, intelligibility, and goodness. As the ultimate foundational reality and auto-explicable cause of everything else, God is different in kind, not just degree, from all other beings that are inherently restricted in their intelligibility (e.g., contingent, finite, composite, mutable beings). P.S. I actually know someone who has a really good book defending classical theism, but I’m not going to tell you his name.

• Metaphysical dependence: Reality exhibits a layered structure with nested causal hierarchies, where less fundamental things depend on more fundamental things—similar to how a waltz is grounded in the dancers and their movements. God is the most fundamental, with all other primary existents (substances) grounded in God’s will.

• The human person: A human being is a hylomorphic compound of matter and form, with the human soul being the (rational) form of the body. Every human person has an immaterial aspect—the intellect. Thomists maintain that hylomorphism is the correct way to understand the human person and human mind, avoiding the extremes of substance dualism and reductive physicalism.⁴

• Libertarianism. Thomism is not just Calvinism under a different name. For Thomists, our actions—including our free actions—are both 100% up to us and 100% up to God, due to 1) the reality of secondary causes and 2) divine universal causality. This account ultimately offers a robust understanding of libertarian agency and, in my view, is the best way to make sense of grace, freedom, and predestination (while avoiding the obvious failures of Molinism, Calvinism, etc.). Those who think Thomism is a form of determinism often misunderstand Thomas's wider metaphysical commitments. They tend to mistakenly assume that God is a cause in the same way that we are causes—which is false! In fact, Thomas's distinction between primary and secondary causality, along with his nested series of synchronic (metaphysical) causes, avoids this issue. As Matthews Grant has convincingly shown, the scholastic metaphysical system—especially its commitment to divine simplicity—may be the only framework capable of securing libertarian freedom without abandoning divine universal causality.

• Epistemological (immediate) realism: Knowledge is actual and definable, not bound by language or culture. It is achieved by re-presentation of form.

These are just some of the positive commitments Thomists hold. As card-carrying members of Big Tent Platonism, Thomism can also be understood by what it opposes—namely, reductionism, materialism, skepticism, relativism, mechanism, and nominalism.

But I’ve probably said enough for one day—hopefully enough to give a general picture of what the contemporary Thomist is committed to. For a little more on what Thomists affirm, including certain theological positions, see this video.

A Thomistic Reading List

For those wanting to go further, here are some books, in no particular order, that I highly recommend for understanding the thought of Thomas Aquinas across a range of issues, including the existence of God, philosophy of nature, morality, epistemology, philosophy of mind, the problem of suffering, etc.