Twelve branches of philosophy explained clearly and systematically in the Thomistic tradition — from logic and metaphysics to ethics and natural theology.
In philosophy, we pursue the knowledge of things through their highest causes using the human intellect alone. This site presents Msgr Glenn's complete seminary course — twelve books covering every branch of philosophy a student needs before theology.
Each branch maps to one of Glenn's seminary manuals. Primary sources by Aquinas, Anselm, Augustine, and others are linked in context throughout.
What is philosophy? Its nature, divisions, and relationship to theology and the sciences.
Begin readingThe art of correct reasoning. Terms, propositions, syllogisms, and valid argument.
Begin readingCan we know truth? The certitude of knowledge and the refutation of scepticism.
Begin readingThe study of being as being. Substance, act and potency, essence and existence.
Begin readingThe philosophy of nature. Matter, form, change, and causality.
Begin readingThe philosophy of mind. Sensation, intellection, the will, and the human soul.
Begin readingThe philosophy of God. The proofs for God's existence, His nature and attributes.
Begin readingMoral philosophy. The good, the virtues, natural law, conscience, and human flourishing.
Begin readingThe family, the state, authority, rights, duties, and the common good.
Begin readingA survey of all major systems from the pre-Socratics to the moderns.
Begin readingThe philosophy of the Catholic religion. Rational grounds for faith.
Begin readingAn accessible guide to the Summa Theologica — the bridge into theology.
Begin reading"The slenderest knowledge that may be obtained of the highest things is more desirable than the most certain knowledge obtained of lesser things."— St Thomas Aquinas, Summa Theologica I, Q.1, Art.5
The Penny Catechism gives the simple answer.
Pohle-Preuss gives the systematic treatment.
Glenn explains the philosophical reasoning.