Rationalism and empiricism were two philosophical schools of the 17th and 18th centuries that expressed opposing views on certain subjects, notably knowledge. Although the debate between the rationalist and empiricist schools had no relation to the study of psychology at the time, it contributed greatly to facilitating the possibility of establishing the discipline of psychology. This essay will describe the empiricist and rationalist debate and relate this debate to the history of psychology. The debate between rationalist and empiricist philosophers concerns the nature of knowledge, and more particularly the way in which we acquire this knowledge. Rationalists and empiricists have opposing, and sometimes mutually exclusive, views on how knowledge is obtained. Rationalism is based on the assumption that all human beings are intrinsically rational. French and German rationalist philosophers, such as Decartes, Spinoza, Leibniz, and Kant, believed that fundamental metaphysical questions could be answered through reason alone. In his work Discourse on Method, Decartes attempted to arrive at a set of fundamental principles, and thus arrive at true knowledge; to do this, he methodologically rejected everything he could doubt. Decartes summarized his conclusion by saying “I think therefore I am” (Decartes, 1637); he concluded that only thought exists, and because thought could not be separated from him, he also concluded that he exists. This conclusion that only the existence of thought cannot be doubted led to the idea that reason and thought are the nature of the soul and that humans are fundamentally rational, constitutes the foundation of thought rationalist. According to rationalist philosophers, reason is what separates man... middle of paper... a body. (G. MacDonald Ross, Trans.). Accessed December 1, 2011: http://www.philosophy.leeds.ac.uk/GMR/hmp/texts/modern/descartes/body/body.html George Boeree, C. (2000). Modern philosophy: the Enlightenment. Accessed December 1, 2011: http://webspace.ship.edu/cgboer/empvsrat.html Kumar Singh, A. (1991). The Complete History of Psychology. Delhi, India: Motilal Banarsidass Publishers PVT. Accessed December 1, 2011: http://books.google.ieLeibniz, GW (1714). Monadology. (R. Latta, Trans.). Accessed December 1, 2011: http://www.rbjones.com/rbjpub/philos/classics/leibniz/monad.htmLocke, J. (1690). An attempt at human understanding. Accessed December 1, 2011: http://www.gutenberg.org/catalog/world/readfile?fk_files=1477354 Richards, G. (2010). Putting psychology in its place: critical historical perspectives (3rd ed.). London: Routledge.