The great historian of ideas, Arthur Lovejoy (1940), referred to ideas as “potent,” “stubborn,” and “migratory,” making the study of ideas and their development complicated, nonlinear, and unpredictable. Philosophic systems are a complex body of interrelated ideas that can engender dynamic intellectual movements. The movements sometimes ebb and flow and sometimes exert themselves in unexpected ways on human thought and life. The more a philosophic system is developed, the more likely it is to become distant from the specific doctrines and formulations of its originator. Cartesianism is no exception. During the second half of the seventeenth century, the philosophy originated by René Descartes (1596–1650) dominated the intellectual life of France and beyond. It was a period that saw the most dynamic challenges, defenses, debates, and developments of Descartes’ ideas. While the legacy of the Cartesian philosophy remains today, a sense of its once vibrant and dynamic power has given way to popularized caricatures.

Cartesianism itself is not a clearly defined system of thought, though its proponents characteristically defend Descartes’ substance-mode ontology, his view that thought is the essence of mind and extension the essence of body, and his view that ideas represent objects external to the mind in a nonresembling way, to name just a few of his main doctrines. Descartes is famous for having argued that the starting point of all certain knowledge is the cogito, “I think, therefore I am,” and that the mind and body are really distinct. It would seem that any genuine Cartesian should at least espouse these views. However, with the exception of Descartes’ view that thought is the essence of mind, there seems to be no single view, argument, or doctrine that escapes rejection at the hands of a genuine Cartesian.

Not much history is required to see that there is no single doctrine or set of doctrines whose interpretation yields a unique identification of Cartesianism. The classic treatment of the history of Cartesianism is Francisque Bouillier's Histoire de la philosophie cartésienne (1868).