Joseph Bobik is Professor of Philosophy at the University of Notre Dame. He is the author of numerous books, including Aquinas on Being and Essence (Notre Dame Press, 1988).

"This book offers a translation of Aquinas's De Principiis Naturae (circa 1252) and De Mixione Elementorum (1273) accompanied by a continuous commentary, followed by two essays: "Elements in the Composition of Physical Substances" and "The Elements in Aquinas and the Elements Today." The unity of the volume rests in the question of the composition of natural things (whether out of matter and form, or out of the elements). . . . Bobik's translation is remarkably clear." —The Review of Metaphysics"Bobik gives a quick, easily digestible translation and discussion of Aquinas' physical theories, most suitable for those with a prevailing interest in the Thomistic worldview." —Philosophy in Review"This work is a companion to Bobik's earlier translation and commentary on Aquinas's On Being and Essence. The Principles of Nature introduces the reader to the basic Aristotelian principles such as matter and form, the four causes so fundamental to Aquinas's philosophy. On Mixture of the Elements *examines the question of how the four elements (earth, air, fire, and water) remain within the physical things composed from them. Bobik gives probably the first published English translation of this work by Aquinas. He includes a section that puts some of the issues raised into a broader context by relating Aquinas's theory both to modern physics, especially the Big Bang theory, and to the work of a little-known medieval Jewish philosopher, Nahmanides." —Religious Studies Review*"Congratulations and thanks to Joseph Bobik for having provided a translation that is both accurate and readable of Thomas's De principiis naturae and De mixitone elementorum." –The Thomist". . . Joseph Bobik offers some genuine, straightforward, and unencumbered philosophy using the words of Thomas Aquinas as a point of departure. Aquinas on Matter and Form and the Elements is 'must' reading for all scholars and students of the works of Thomas Aquinas." —The Midwest Book Review