Catholic Treasury Network

The Twelve Branches

Catholic philosophy in the Thomistic tradition divides into twelve branches. Each one is presented here from Msgr. Paul J. Glenn's seminary course, with primary sources from Aquinas, Anselm, Augustine, and others linked in context.

I
Introduction to Philosophy
Introduction · 1944

What philosophy is, what it studies, and its relationship to faith and the other sciences.

32 chapters
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II
Logic
Dialectics · 1940

Terms, propositions, syllogisms — the art of correct reasoning.

19 chapters
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III
Epistemology
Criteriology · 1937

Can we know truth? The certitude of knowledge and the refutation of scepticism.

30 chapters
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IV
Metaphysics
Ontology · 1939

The study of being. Substance, act and potency, essence and existence.

17 chapters 1 source
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V
Cosmology
Cosmology · 1941

The philosophy of nature. Matter, form, change, and causality.

17 chapters
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VI
Philosophical Psychology
Psychology · 1936

The philosophy of mind. Sensation, intellection, the will, and the soul.

26 chapters
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VII
Natural Theology
Theodicy · 1939

The philosophy of God. Proofs for God's existence and the divine attributes.

18 chapters 1 source
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VIII
Ethics
Ethics · 1930

Moral philosophy. The good, the virtues, natural law, conscience.

28 chapters
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IX
Social Philosophy
Sociology · 1941

Family, state, authority, rights, duties, the common good.

19 chapters
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X
History of Philosophy
History of Philosophy · 1929

A survey of all major systems from the pre-Socratics to the moderns.

60 chapters
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XI
Apologetics
Apologetics · 1931

The philosophy of the Catholic religion. Rational grounds for faith.

30 chapters
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XII
Tour of the Summa
Tour of the Summa · 1960

An accessible guide to the Summa Theologica — the bridge into theology.

Awaiting PD 2028
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