Cartesianism is the philosophical and scientific system of René Descartes and its subsequent development by other seventeenth century thinkers, most notably François Poullain de la Barre, 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, philosophy was a thinking system that embodied all knowledge.
Aristotle and St. Augustine’s work influenced Descartes's cogito argument. Additionally, there is similarity between Descartes’s work and that of Scottish philosopher George Campbell’s 1776 publication, titled Philosophy of Rhetoric. In his Meditations on First Philosophy he writes, "[b]ut what then am I? A thing which thinks. What is a thing which thinks? It is a thing which doubts, understands, [conceives], affirms, denies, wills, refuses, which also imagines and feels."
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. To this point Descartes wrote, "we should conclude from all this, that those things which we conceive clearly and distinctly as being diverse substances, as we regard mind and body to be, are really substances essentially distinct one from the other; and this is the conclusion of the Sixth Meditation." Therefore, we can see that, while mind and body are indeed separate, because they can be separated from each other, but, Descartes postulates, the mind is a whole, inseparable from itself, while the body can become separated from itself to some extent, as in when one loses an arm or a leg.