“René Descartes (1591-1650), like Bacon, follows Machiavelli in orienting knowledge to the acquisition of the power to “promote as far as possible the general good of mankind.” In his Discourse on Method he preferred the clear and distinct ideas of geometry with its certain conclusions to all other forms of knowledge. He tried to set all knowledge on the sure and firm foundation of certainty, arguing that we should suspect as false anything we think we know that can be doubted. His “method of universal doubt” stats the Enlightenment “prejudice against prejudice.” His “I think therefore I am” (cogito ergo sum) is supposed to prove his own existence as a thinking being and becomes the basis for the certain foundations of all knowledge, which includes two kinds of substance: non-corporeal (thinking beings, subjects) and corporeal (extended things, objects). Beginning from the knowledge he finds in himself, he proceeds to the “book of nature” outside him to build up an edifice ofknowledge with a certainty that is supposed to equal that of geometrical demonstration (the key to which is clear and distinct perception by reason independently of sense experience). The purpose of such knowledge, however, is “to make man the master and possessor of nature” (Frederick Lawrence, Philosophers and Theologians, Boston College).