"The majestic elaboration of thought manifested in St. Thomas's work," says Josef Pieper, consists partly "in the fact that the theological wisdom of the earliest Christian centuries is interwoven with the philosophical heritage of the Greek world." In his Summa Theologica, we find not only a masterful synthesis of Aristotle and the Bible, but also a "genuine conversation or dialogue" with the greatest minds of philosophy and theology, including Plato and St. Augustine, Cicero and St. Ambrose. "St. Thomas is, in effect, placing himself within the stream of traditional truth nourished by the past; without claiming to give a final solution, he leaves the way open for future quest and discovery as that stream flows onward toward the yet unknown." Students of political philosophy have much to gain from the Summa, a book written "for the instruction of beginners," and whose influence on subsequent theory and practice in religion, politics, culture, and law has been immeasurable. At 3,000 pages, however, it can be difficult to navigate for the modern reader. This volume contains a selection of passages carefully chosen to give us direct access to Aquinas's main arguments on ethics (including human nature, psychology, happiness, virtue, and natural law) and politics (including human law, the political regime, and justice), as well as those theological questions most closely related to his political thought. It thereby seeks to reopen the way to this stream of insights into the nature of and means of achieving truth, justice, and the common good.