How did Descartes believe limbs were moved?

Descartes proposed that limbs were moved through the flow of "animal spirits," a concept he developed in the 17th century. He believed that these spirits were fine particles, akin to a gas, that flowed through the body and were responsible for facilitating movements by interacting with the muscles and nerves. Descartes viewed the body as a complex machine; he thought that the brain produced these animal spirits, which then traveled through the nervous system to affect muscular action.

This idea was significant because it was one of the early attempts to explain movement in a mechanistic way, laying foundational thoughts for later theories of physiology and psychology. The notion of animal spirits demonstrates Descartes’ vision of a link between the immaterial mind and the material body, paving the way for more sophisticated understandings of neuromuscular activity in modern science.