This book is a revised and expanded edition of three lectures delivered by the author at Wake Forest University in 1979. Long out of print, in its new edition it should be a valuable resource for scholars and teachers of thephilosophy of religion. The first two lectures, after a critique of the incompleteness of St. Thomas Aquinas's famous Five Ways of arguing for the existence of God, explore lesser-known resources of Aquinas's philosophical ascent of the mind to God: the unrestricted dynamism of the human spirit as it reaches toward the fullness of being, and the strictly metaphysical ascent to God from finite to infinite, in the line of Aquinas's later, more Neoplatonicallyinspired, metaphysics of participation.The third, and most heavily revised, lecture is a critique of Whitehead's process philosophy, distinguishing Aquinas more sharply and critically from Whitehead than in the first edition.