Summa Theologica - Part I Q46-50: Of the Beginning of the Duration of Creatures - Of the Substance of the Angels Absolutely Considered

The Summa Theologica (or the Summa Theologiae or simply the Summa, written 1265–1274) is the most famous work of Thomas Aquinas although it was never finished. It was intended as a manual for beginners as a compilation of all of the main theological teachings of that time. It summarizes the reasonings for almost all points of Christian theology in the West, which, before the Protestant Reformation, subsisted solely in the Roman Catholic Church. The Summa's topics follow a cycle: the existence of God, God's creation, Man, Man's purpose, Christ, the Sacraments, and back to God. (Summary adapted from the Wikipedia)

 46. Of the Beginning of the Duration of Creatures

 47. Of the Distinction of Things in General

 48. The Distinction of Things in Particular

 49. The Cause of Evil

 50. Of the Substance of the Angels Absolutely Considered