Inspired by the ideas contained in the newly recovered ancient sources, Renaissance humanists questioned the traditional teachings of universities. Humanistically trained physicians, called “medical humanists,” were particularly active in the field of natural philosophy, where alternative approaches were launched and tested. Their intellectual outcome contributed to the reorientation of philosophy toward natural questions, which were to become crucial in the seventeenth century. This volume explores six medical humanists of diverse geographical and confessional origins (Leoniceno, Fernel, Schegk, Gemma, Liceti and Sennert) and their debates on matter, life and the soul. The study of these debates sheds new light on the contributions of humanist culture to the evolution of early modern natural philosophy.