The issue of how knowledge is possible and what knowledge can be considered true and what false is a key one addressed by both Gottfried Leibniz and RenT Descartes, and in considering what can be known and what can be assumed to be true, both also address the question of the perfection of God and are faced with the need to deal with this perfection in offering proofs of their respective metaphysical views. Leibniz accepted aspects of the Cartesian system while rejecting certain elements considered to be errors. The main structure, however, was to be adapted by Leibniz with a transcendent god.
Descartes accepted the reality and truths of mathematics and attempted to find that which existed in the world that could be demonstrated with scientific and mathematical certainty. Descartes was seeking absolute certainty.
The problem of knowledge is a key one in philosophy, asking as it does whether there is anything we can really know and whether what we know can be said to be objectively true. Theories of knowledge come under the heading of epistemology. We perceive the world through our sense, but our senses can be deceived. The degree of deception involved also varies according to different views of the world. Some see this deception as absolute and deny that there can be any knowledge at all through the senses. Others admit knowledge acquired through the senses while recognizing that there are limitations. RenT Descartes was a rationalist, and his thinking was governed by his knowledge of and dedication to mathematics, which he believed could clear up the confusions and uncertainties of philosophy. In this regard, Descartes wished to attain certainty with reference to the external, physical objects in the world around us. Mathematics, he believed, could help philosophy achieve absolute certainty so that philosophy could then reach final and certain truth. He began with the now well-known proposition, "I think, therefore...