The Quinque viæ, Five Ways, or Five Proofs are Five arguments regarding the existence of God summarized by the 13th century Roman Catholic philosopher and theologian St. Thomas Aquinas in his book, Summa Theologica. They are not necessarily meant to be self-sufficient “proofs” of God’s existence; as worded, they propose only to explain what it is “all men mean” when they speak of “God”. Many scholars point out that St. Thomas’s actual arguments regarding the existence and nature of God are to be found liberally scattered throughout his major treatises, and that the five ways are little more than an introductory sketch of how the word “God” can be defined without reference to special revelation (i.e., religious experience).
The five ways are; the argument of the unmoved mover, the argument of the first cause, the argument from contingency, the argument from degree and the teleological argument. The first way is greatly expanded in the Summa Contra Gentiles. Aquinas left out from his list several arguments that were already in existence at the time, such as the ontological argument of Saint Anselm, because he did not believe that they worked. In the 20th century, the Roman Catholic priest and philosopher Frederick Copleston, devoted much of his works to fully explaining and expanding on Aquinas’ five ways.
The arguments are designed to prove the existence of a monotheistic God, namely the Abrahamic God (though they could also support notions of God in other faiths that believe in a monotheistic God such as Sikhism, Vedantic and Bhaktic Hinduism), but as a set they do not work when used to provide evidence for the existence of polytheistic, pantheistic, panentheistic or pandeistic deities.