Philosophy · Medieval & Early Modern Philosophy
A topic within Medieval & Early Modern Philosophy, itself one of 12 topics in that field and part of Philosophy.
No prior grounding assumed.
Proslogion
Anselm of Canterbury · 1078
Defines God as that than which nothing greater can be conceived, and argues that a being meeting this definition must exist in reality and not only…
Assumes you know the vocabulary.
On Being and Essence
Thomas Aquinas · 1254
Distinguishes what a thing is from the separate fact that it exists, and argues only God is a being whose essence and existence are identical, with…
Primary sources and full treatments.
Summa Theologica
Thomas Aquinas · 1265
Synthesises Aristotelian philosophy with Christian doctrine, arguing reason and revelation cannot conflict because both ultimately come from the same…
3 works
Anselm of Canterbury
Defines God as that than which nothing greater can be conceived, and argues that a being meeting this definition must exist in reality and not only in the mind — the first ontological argument.
link checked 17 Sept 2026Thomas Aquinas
Distinguishes what a thing is from the separate fact that it exists, and argues only God is a being whose essence and existence are identical, with everything else receiving its existence from outside itself.
link checked 17 Sept 2026Thomas Aquinas
Synthesises Aristotelian philosophy with Christian doctrine, arguing reason and revelation cannot conflict because both ultimately come from the same God, and offers five ways to argue for God's existence from observed features of the world.
link checked 17 Sept 2026