The five Ways.
St. Thomas Aquinas, Five Ways, Summa Theologiae
The Five Ways are five proofs or demonstrations that Aquinas offers near the beginning of his Summa theologiae to establish the existence of God. Although the Five Ways compose only a miniscule portion of Aquinas's Summa-less than 775 words, or nearly one word for every fourth page in a standard edition of the work one would be hard-pressed to find another part of Aquinas's corpus that has been commented on as much as the Five Ways. Yet despite their minute size and the gigantic secondary literature on them throughout the centuries, whether Aquinas succeeds-and even what it is that Aquinas is attempting to do: how he intends to do it-is still debated.
B. Davies & E. Stump (Eds.), The Oxford handbook of Aquinas