This chapter introduces the notion of “diachronic mechanism” to account for experimental approaches to living phenomena that were developed in Spinoza’s circle in the late seventeenth-century. This notion of “diachronic mechanism” allows me to distinguish two compatible types of mechanistic explanations: the well-known synchronic mechanistic explanations, which explain organic functions through the reduction of organisms into smaller components, and what I propose to call “diachronic mechanism,” which focuses on the temporal aspect of organic modifications. This diachronic mechanism describes organic modifications as a continuous series of physical events without specifying the inner structure of the parts which initiate the process. As a consequence, a new kind of analogy between automata and human beings is developed. It shifts the emphasis towards an experimental approach to the interactions between bodies and their environment.