Named Doctor of the Church by Pope Pius IX, St. Hilary was a gifted orator, a zealous Christian philosopher, and a defender of orthodoxy. He often did theological battle with the Anomoeans and the Semi-Arians, and traveled across Europe to bring the local bishops out of the hold of Arianism. Here, twelve books on the Trinity by St. Hilary are compiled, bringing his thoughts together on the deity, sonship, and interrelationship of God.