Cartesianism is the name given to the philosophical and scientific system of René Descartes and its subsequent development by other seventeenth century thinkers, most notably Nicolas Malebranche and Baruch Spinoza. Descartes is often regarded as the first thinker to emphasize the use of reason to develop the natural sciences. For him, the philosophy was a thinking system that embodied all knowledge, and expressed it in this way:
Cartesians view the mind as being wholly separate from the corporeal body. Sensation and the perception of reality are thought to be the source of untruth and illusions, with the only reliable truths to be had in the existence of a metaphysical mind. Such a mind can perhaps interact with a physical body, but it does not exist in the body, nor even in the same physical plane as the body. The question of how mind and body interact would be a persistent difficulty for Descartes and his followers, with different Cartesians providing different answers.