Summa Theologica - Part I Q42-45: Of Equality and Likeness among the Divine Persons - The Mode of Emanation of Things from the First Principle

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)

 42. Of Equality and Likeness among the Divine Persons

 43. The Mission of the Divine Persons

 44. The Procession of Creatures from God, and of the First Cause of All Things

 45. The Mode of Emanation of Things from the First Principle