The Five Ways: St Thomas Aquinas' Proofs of God's Existence

Anthony Kenny's examination of Aquinas's Five Ways represents a significant analytical intervention in twentieth-century philosophy of religion. This monograph subjects Thomas Aquinas's celebrated proofs for God's existence to rigorous philosophical scrutiny, employing the tools of contemporary analytic philosophy to assess medieval arguments that have shaped Western theological discourse for seven centuries.

Kenny approaches the Five Ways—the arguments from motion, causation, contingency, degrees of perfection, and teleology—with careful attention to their logical structure and metaphysical presuppositions. His analysis demonstrates particular concern with the validity of these arguments when translated into modern philosophical idiom. The work systematically examines each proof, identifying points where Aquinas's reasoning depends upon Aristotelian physics or metaphysical assumptions that contemporary philosophy finds problematic. Kenny's method combines historical sensitivity with philosophical critique, acknowledging the sophistication of Aquinas's thought while questioning whether the arguments succeed on their own terms.

The monograph engages critically with both neo-Thomist defenders of the Five Ways and their secular critics. Kenny challenges interpretations that too readily dismiss Aquinas as relying on outdated science, while simultaneously resisting attempts by contemporary Thomists to rehabilitate the proofs through creative reinterpretation. His analysis reveals how certain moves in Aquinas's arguments—particularly the transition from contingent beings to a necessary being—involve logical leaps that remain philosophically contentious.

Kenny's contribution extends beyond mere criticism to illuminate the continuing philosophical significance of natural theology. By showing where Aquinas's proofs encounter genuine philosophical difficulties, the work helps clarify what successful theistic argumentation would need to establish. The monograph addresses fundamental questions about causation, necessity, and explanation that remain central to philosophy of religion debates.

This study matters for several reasons. First, it provides one of the most philosophically sophisticated treatments of arguments that continue to influence both academic theology and popular apologetics. Second, Kenny's analysis, coming from a philosopher sympathetic to theism but committed to philosophical rigor, demonstrates how serious engagement with classical theistic proofs can proceed without partisan agenda. Third, the work establishes methodological standards for how contemporary philosophy should approach historical arguments about God's existence, neither dismissing them as antiquated nor accepting them uncritically.