A professor, biologist, and physiologist argues that modern Darwinism's materialist and mechanistic biases have led to a scientific dead end, unable to define what life is-and only an openness to the qualities of "purpose and desire" will move the field forward. J. Scott Turner contends, "To be scientists, we force ourselves into a Hobson's choice on the matter: accept intentionality and purposefulness as real attributes of life, which disqualifies you as a scientist; or become a scientist and dismiss life's distinctive quality from your thinking. I have come to believe that this choice actually stands in the way of our having a fully coherent theory of life." Growing research shows that life's most distinctive quality, shared by all living things, is purpose and desire: maintain homeostasis to sustain life. In Purpose and Desire, Turner draws on the work of Claude Bernard, a contemporary of Darwin revered among physiologists as the founder of experimental medicine, to build on Bernard's "dangerous idea" of vitalism, which seeks to identify what makes "life" a unique phenomenon of nature. To further its quest to achieve a fuller understanding of life, Turner argues, science must move beyond strictly accepted measures that consider only the mechanics of nature.