Thomas Aquinas (1224/6-1274) was first and foremost a Christian theologian. Yet he was also one of the greatest philosophers of the Middle Ages. Drawing on classical authors, and incorporating ideas from Jewish and Arab sources, he came to offer a rounded and lasting account of the origin of the universe and of the things to be found within it, especially human beings. Aquinas wrote many works, but his greatest achievement is undoubtedly the _Summa Theologiae_. This presents his most mature thinking and is the best introduction to his philosophical (and theological) ideas. Few secondary books on Aquinas focus solely on the _Summa_, but the present volume does just that. Including work by some of the best Aquinas scholars of the last half decade, it provides a solid introduction to one of the landmarks of western thinking.