The French philosopher, Rene Descartes (1596-1650), approached knowledge from quite a different stance than did John Locke. For Descartes, man has ultimate knowledge of his own existence because he is a thinking being – cogito ergo sum – "I think, therefore I am." Thus the foundations of knowledge consist of a set of first, "self-evident" principles, a priori principles. The mind is not an empty cabinet but is filled with universal, though not readily known, principles. Access to these first principles is not based on "the fluctuating testimony of the senses" nor on the "blundering constructions of imagination." Descartes distrusted sensory evidence as much as he avoided undisciplined imagination. The first principles are those based on "the conception which an unclouded and attentive mind gives." It is conception "wholly freed from doubt," principles derived from clear and logical thought. From these first principles, other truths can be deduced by a rigorous application of logical rules and axioms. Knowledge is not so much what corresponds to experience but what has coherency within and among the principles and their deduced statements. And so the deductive and rational methods are born. Descartes published his approach to knowledge in 1637, in Discourse on Method. The rationalist begins with a set of assumptions that are hypothetically true. For instance, Jericho is a community settled by people. The walls of Jericho are defensive walls. Defense is an activity for defending something. All of these assumptions need not be verified by observation, need not exist in fact. They need only be hypothetically correct. Implicit from these assumptions, a deduction can now be made logically. The people of Jericho have something to defend. Mathematically-rigorous formulas are applied in order to arrive at the deductions. The strength and legitimacy of the rational method is its ability to objectively think about the natural world and deduce…