Same Machine, Different Structure: Animal-Plant Analogy in Cartesian Mechanical Physiology

The test of the Cartesian mechanism puts in crisis the plant analogy that had just regained momentum in early modernity. By representing the living body as a machine, Descartes (apparently) sacrificed the study of plants in his natural philosophy. However, when his mechanistic analogy lags behind his physiological explanation, the comparison between plants and animals resurfaces and reveals its originality. First, Descartes defines plants as hydraulic machines (just like animals); second, he uses the animal explanation to describe plants; third, he describes structural differences between living bodies. If the same mechanical laws are applicable to bodies, a mechanical gradation unfolds between plants and animals. Then the Cartesians in turn assume the same distinction when they propose a plant-animal analogy as part of the philosophical mechanism that determines modern culture.