Two New Books on the Five Ways

My colleague, Dan Bonevac, and I are putting the final touches on two manuscripts about Thomas Aquinas’s Five Ways. One is designed for an academic press, and the other for a more popular or “trade” press. We think that the first will probably be appearing in late 2026, and the other a few months later.

Thomas Aquinas’s Five Ways of proving God’s existence constitute a very small part of Thomas’s oeuvre, but they are by far the most famous—one might even say, infamous. As frequently interpreted, the Five Ways are terrible arguments, committing elementary logical errors, making unwarranted assumptions, and relying on outdated science. They were in fact summarily ignored or dismissed even by scholastic philosophers such as John Duns Scotus and Francisco Suarez. Among commentators, they had detractors—Petrus Aureoli, for example—as well as defenders. In the early modern period, René Descartes avoided them completely, seeking other ways of demonstrating God’s existence (Agostini 2015), and David Hume and Immanuel Kant attacked them so brutally that their reputation has yet to recover. Five Ways defenders over the last century such as Etienne Gilson, Reginald Marie Garrigou-Lagrange, Frederick Copleston, and Edward Feser have unfortunately had limited impact outside Thomist circles.

The interpretation of some of the Five Ways, specifically, the First, Second, and Fifth, became fixed early on. There has been relatively little dispute about how to interpret these three arguments. The First Way, the argument from motion, has largely been abandoned, and the Second Way, the argument for a first cause, has had its place largely supplanted by the argument from contingency as developed by Scotus, Leibniz, and Samuel Clarke. The Fifth Way has often been taken to be an early version of the argument from design, masterfully discredited by Hume.

Many Thomists, even the most ardent, have found the remaining two proofs, the Third and Fourth, to be sources of embarrassment in light of their many seeming defects. Some late Medieval and Renaissance commentators omit the Third Way altogether.

Taken as a whole, then, the Five Ways have substantially damaged Thomas’s reputation as a philosopher. To the extent that later Thomists attempted to defend these arguments, the damage to reputation extends to the entire Thomistic tradition.

We propose to give the Five Ways another look. The late 20^th and early 21^st century have seen a remarkable revival of Aristotelian philosophy in ethics, epistemology, philosophy of biology, and metaphysics. It is time to reconsider Aristotelian natural theology.