The Essential Philosophical Passages of Saint Thomas Aquinas’ Summa Theologica A shortened version of Kreeft’s much larger Summa of the Summa , which in turn was a shortened version of the Summa Theologica . The reason for the double shortening is pretty obvious: the original runs some 4000 pages! (The Summa of the Sum Memoria Press product: https://www.memoriapress.com/curriculum/classical-studies/a-shorter-summa/