Leon Kass is the Addie Clark Harding Professor of Social Thought and in the College at the University of Chicago. He is the author of several books, including, Toward A More Natural Science: Biology and Human Affairs; The Hungry Soul: Eating and the Perfecting of our Nature; Life, Liberty, and the Defense of Dignity: The Challenge for Bioethics; and The Beginning of Wisdom: Reading Genesis. Trained as a physician and biologist, Kass has taught on humanistic subjects for most of his career. He has also taken periodic government positions, most recently as chair of the President's Council on Bioethics.

Kass's positions are rather conservative. He generally views biomedical innovations with extreme suspicion; life-extending technologies are, in his eyes, often dangerous, for they discourage careful thought and deliberate, valuable action. Kass strongly opposes stem cell research and has even produced arguments against in vitro fertilization.