Book excerpt: Jacques Maritain (1882-1973) was a Neo-Thomist philosopher who taught in France and the United States and was French Ambassador to the Vatican from 1945-48. A Protestant who became a Roman Catholic through association with Leon Bloy, he devoted himself to the study of Thomism and its application to all aspects of modern life and urged Christian involvement in secular affairs. An Introduction to Philosophy is perhaps the most well-known and enduring of all Maritain's many books. It offers a clear and highly readable introduction to the philosophies of both Aristotle and St Thomas Aquinas.