Thomism

Thomism is the philosophical school that arose as a legacy of the work and thought of Saint Thomas Aquinas, philosopher, theologian, and Doctor of the Church. In philosophy, his commentaries on Aristotle are his most lasting contribution. In theology, his Summa Theologica was one of the most influential documents in medieval theology and continues to be studied today in theology and philosophy classes. In the encyclical Doctoris Angelici Pope Pius X cautioned that the teachings of the Church cannot be understood without the basic philosophical underpinnings of Thomas' major theses:

The capital theses in the philosophy of St. Thomas are not to be placed in the category of opinions capable of being debated one way or another, but are to be considered as the foundations upon which the whole science of natural and divine things is based; if such principles are once removed or in any way impaired, it must necessarily follow that students of the sacred sciences will ultimately fail to perceive so much as the meaning of the words in which the dogmas of divine revelation are proposed by the magistracy of the Church.

The Second Vatican Council described Thomas's system as the "Perennial Philosophy".