This project aims to produce a ‘counter-history’ of biology in which the focal point is vitalism in its successive incarnations and definitions. Vitalism has classically been taken to be the most extreme, supernaturalist position regarding the uniqueness of biological entities, beyond the pale for mainstream biological science. But careful historical scholarship reveals the existence of different forms of vitalism, some of which are deeply interwoven with developments in medicine, physiology and experimental biology. This project will investigate how vitalism is actively present in four key developments in biology. The first is the emergence of the concept of organism in the early Enlightenment; the second is the late eighteenth century emergence of biology as a science; the third is the development of (experimental) physiology in nineteenth-century France and Germany; and the fourth is the shift to a more “philosophical” and “theoretical” form of vitalism in the twentieth century. Such historical work yields a new vision of biology as a science and prospects for theoretical biology and philosophy of biology, given renewed interest in questions such as ‘what is a biological individual?’ and ‘what is life?’ in a post-genomic era.