Unlike Aristotelian physics with its Ideological notions, modern physics was developed exclusively in relation to the nonliving domain. This raised the question as to whether mechanics applies to organisms, and if so, to what extent. From the seventeenth century on, mechanistic ideas became prominent in biological and medical theory. Contemporary biology explains essential features of life on the basis of physical laws and processes. This does not prove, however, that the early mechanists were essentially right. In the eighteenth century, following Cartesian notions of mind-body separation and preformation theories of organismic development, they tended to exclude major biological questions rather than answering them. It was those who insisted on the organizational features of organisms, like Stahl and Wolff, who paved the way for solutions to such crucial problems as the psychological basis of human nature and behavior and the generation of form in the course of reproduction. Though they underrated the potentials of a future, extended physics for understanding biology, their case against reductionist exclusion should not be considered outdated even today.