Frequently Asked Questions

Philosophy proceeds by unaided natural reason alone; theology proceeds from revealed premises accepted on faith. The two can treat the same object — God’s existence, for instance — but by entirely different methods and evidence.

Start with Glenn’s Introduction. It runs through the whole course in miniature — the operations of the mind, certitude, being, the bodily world, life, God, ethics — so that by the end you know what each branch is for and which one you actually want. Logic is the usual second stop, since every other branch uses it.

One school, though the one the Church has consistently commended for seminary formation. Scotists, Suarezians and the Augustinian tradition are all Catholic philosophers in good standing and disagree with Aquinas on real questions. This site is Thomist because Glenn was, and it says so rather than presenting one school’s conclusions as the Catholic position.

The syllogism makes explicit the structure every valid argument already has implicitly. Training in it sharpens the ability to spot bad reasoning — equivocation, false premises, invalid form — wherever it appears, including in ordinary speech.

Validity is a property of the form: if the premises were true, the conclusion would have to follow. Truth is a property of the content. An argument can be perfectly valid and still reach a false conclusion from a false premise, which is why Dialectics (correctness of inference) and Criteriology (truth of content) are treated as two branches and neither is complete alone.

Not the same notation, and not quite the same object. Modern logic formalises relations between propositions; Aristotelian logic is built around the term and the idea behind it, which is why it feeds directly into metaphysics. The two are largely compatible, but only the older one is designed as a preparation for the questions the rest of this course asks.

Glenn’s course (Criteriology) argues that universal scepticism is self-refuting — to argue against the reliability of reason is already to use reason and trust it. From there it defends the basic reliability of sense knowledge and intellectual first principles.

No. Certitude is the firm assent of the mind to a judgment on evidence that excludes reasonable fear of error; the feeling of confidence may accompany it or may be entirely absent. Glenn distinguishes degrees of it — metaphysical, physical and moral — precisely so that a claim can be assessed by the kind of evidence it rests on rather than by how strongly anyone happens to hold it.

By abstraction. The senses deliver a particular image; the intellect draws from it a universal that is not itself a particular — “triangle”, “justice”, “cause” — and a universal has no size, colour or location. That the mind performs an operation the senses cannot is the hinge of the whole argument, and it is treated at length in Philosophical Psychology.

Every other science studies some restricted kind of being — living things, quantities, minds. Metaphysics studies what belongs to anything simply insofar as it exists: act and potency, substance and accident, essence and existence.

Essence is what a thing is; existence is that it is. In everything we encounter the two are really distinct — you can know perfectly well what a phoenix is without there being one — which means nothing in our experience accounts for its own being. That is the point at which metaphysics hands the question to natural theology.

Substance is not a claim about what something is made of. It names the way a thing has being — in itself, rather than in something else as a colour or a shape does. Chemistry can give a complete account of a thing’s constituents without touching that question, because it is not the question chemistry asks.

No — philosophical cosmology asks about the nature of change, matter, and form at the most general level (why does anything change at all?), while empirical science measures and predicts particular changes. The two are complementary, not competing.

It is not in competition with it. Hylomorphism is an analysis of what any changeable body must be if change is to be intelligible at all, which is why Glenn sets it against monism, atomism and dynamism rather than against any physical theory. Fields and particles are candidates for what the matter is; they are not answers to why anything can become what it was not.

Philosophy settles whether a miracle is possible; history and theology settle whether a particular one occurred. Cosmology’s contribution is its account of the laws of nature as the ordinary course of created natures rather than as absolute necessities — which is what makes an exception conceivable without the world becoming unintelligible.

Philosophical psychology asks a different question than neuroscience: not how the brain processes information, but what kind of thing must exist to explain intellection and free will — a question about nature and causality that empirical method alone cannot settle.

In the philosophical sense, yes: the soul is the principle of life, so anything alive has one. Plants have a vegetal soul and animals a sentient one, and both perish with the body. Only the human soul performs an operation — understanding universals — that no bodily organ can perform, which is the ground for holding it immaterial and therefore not liable to perish with the body.

Freedom here does not mean acting without motives; it means that no particular good presented to the will necessitates the will’s assent, because the intellect can always see the good in question as partial. Character and circumstance genuinely incline, sometimes very heavily. Inclining is not the same as determining, and Glenn’s argument turns on that difference.

They cover much of the same ground — Aquinas’s Five Ways appear in both — but natural theology (Theodicy) treats it as a conclusion of philosophical reasoning, prior to and independent of any appeal to revelation.

The argument does not begin from “everything has a cause”. It begins from things whose existence is not self-explanatory — things in which essence and existence are distinct — and argues that such things cannot be accounted for by an endless series of others in the same condition. What the argument arrives at is precisely something whose essence is to exist, of which the question does not arise.

No, and Aquinas was explicit that reason alone cannot demonstrate that the world began in time. The proofs turn on dependence now rather than on a first moment: a world that had always existed would still be a world of things that do not account for their own being. Cosmology treats the age of the world as a separate question with a separate answer.

Natural law ethics in the Thomistic tradition is argued from human nature and its rational end, without appeal to revelation — it claims to be accessible to any reasoning person, which is precisely why Glenn treats it in the philosophy course rather than the theology tracts.

Because two acts can produce the same outcome while being genuinely different acts. The tradition’s principle of double effect exists to track that difference — between intending an evil and foreseeing it as a side effect — not to dodge hard cases with a technicality.

Natural law holds that personhood tracks what a being is by nature, not which capacities it happens to be exercising at a given moment. On that view a human being possesses a rational nature from the beginning of its existence as an individual organism, even though that nature is only gradually exercised.

By three determinants together: the object (what is done), the circumstances, and the end (why it is done). All three must be good for the act to be good, and a defect in any one of them is enough to spoil it. This is why a good intention cannot make a wrong act right, and why a good act done for a corrupt motive is not virtuous.

Because there are two obligations, not one: to follow conscience, and to form it. A conscience that is mistaken through no fault of one’s own excuses the agent, since he could not have known better. A conscience left mistaken through negligence or convenient incuriosity does not, and the failure to enquire is itself the fault.

Not quite. Subsidiarity holds that a higher body shouldn’t absorb a function a lower one can perform adequately, but it equally obliges the higher body to step in when the lower one genuinely can’t cope — a principle about the right level of action, not a blanket argument for smaller government.

No. The tradition holds two things together: a real right to migrate grounded in the universal destination of created goods, and a real authority of political communities to regulate their own membership for the sake of the common good. Neither cancels the other, and the numbers are left to prudence.

Ethics reaches them as conclusions: having established the moral law and the rights and duties that follow from human nature, it works out what those require in marriage, work and war. Sociology starts from the societies themselves and asks what each is for and how they stand to one another. Same subject matter, approached from opposite ends.

The tradition says both, and distinguishes. Authority as such comes from God, in the sense that man is by nature a social animal and no society can exist without it — it is not a human invention that could be dispensed with. Who holds that authority and in what form is determined by the community, which is why no particular constitution can claim divine sanction.

Aquinas himself engaged seriously with Aristotle, the Platonists, and his contemporaries — seeing where a system goes wrong, and why it seemed plausible, sharpens understanding of the true position far more than being handed conclusions alone.

To mark the boundary rather than to blur it. Glenn surveys the ancient East to show what wisdom literature and religious cosmogony achieved, and then to identify what the Ionians did that was different: asking after the nature of things by unaided reason, and holding the answer open to argument. Philosophy proper begins at that turn.

No. The Stoics, Epicureans and Skeptics, the Alexandrian and Athenian schools, Augustine and the Fathers, and the Arabian and Jewish commentators are all treated at length here — and the last of these is a large part of why the thirteenth century could do what it did. Glenn devotes a chapter to the causes of that flowering rather than presenting it as a sudden recovery.

They overlap but differ in method: this branch treats the rational credibility of religion in general and Catholicism in particular using philosophy alone (miracles, the reasonableness of revelation), while the theology-site tract works from within faith to answer objections to specific doctrines.

Apologetics argues that the claim is credible — from the character of the claimant, from the miracles, from the prophecies — and that argument is historical and philosophical, not an appeal to faith. What it establishes is that believing would be reasonable. The assent of faith itself remains a distinct act, and one the argument cannot compel.

Apologetics does not produce faith and does not claim to. Its work is with the preambles: showing that God can be known, that revelation is possible, that the claim of Christ is credible — clearing the ground so that the act of faith is not an act against reason. What follows is a different kind of act altogether.

It helps, since the Summa draws on logic, metaphysics, and ethics throughout, but Glenn’s Tour is written as an accessible bridge — you can start here and circle back to the earlier branches as needed.

It is designed to be the opposite — a question-by-question précis meant to get you into the text and keep you oriented once you are there. Glenn gives you the shape of the argument; Aquinas gives you the argument. Read the Tour beside the Summa rather than instead of it.

On Catholic Theology, where all of Glenn’s questions are hosted in full. It sits there rather than here because the Tour is the bridge out of philosophy and into theology proper, and it is most useful alongside the tracts it summarises.