Twentieth-century French philosophers Jacques Maritain and Yves R. Simon pioneered new approaches to understanding and defending political democracy in the wake of two world wars. Rather than break from a religious tradition that seemed to struggle against modernity and certain forms of democratic theory and practice, these thinkers instead looked back to the philosophy of Aristotle and Thomas Aquinas to propel Catholic political philosophy forward. The profound influence of Maritain and Simon is manifest in the dramatic achievements of Vatican II and in the work of the scholars of political...