Book excerpt: The existence of God as demonstrated from motion has preoccupied men in every age, and still stands as one of the critical questions of philosophic inquiry. The four thinkers Father Buckley discusses were selected because their methods of reasoning exhibit sharp contrasts when they are juxtaposed. Originally published in 1971. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.