Aquinas on the Trinity: Summa Theologica I Q 27-43 by Thomas Aquinas

St. Thomas was a 13th-century philosopher, theologian, and doctor of the Catholic Church. In his Summa Theologica, Aquinas presents an unrivaled analysis of the doctrine of the Blessed Trinity, the revealed truth that the one God exists in three Divine Persons: Father, Son, and Holy Spirit. The Treatise on the Trinity includes Aquinas’s complete investigation into this mystery of faith (ST I Q 27-43).