One of the most significant qualities of modern epistemology is quantification. The basis of this quantification is undoubtedly internalization of the science of mathematics and geometry in philosophical subjects. In the 17th century, the development of natural sciences and the effect on human being have caused philosophers to change theoretical ground. Hereby, it is seen that the philosophical system has been built according to these sciences. The most important or maybe the initial point of this theory is Descartes. This study deals with how Descartes has integrated mathematics into the philosophical system and reflection as a result of this integration. One the most important aspects of the theoretical construct which Descartes has put forward is that philosophical thought cannot reveal a conclusion without a method. In this manner, it has been widespread that there is a direct proportion between philosophical thought and method. This idea has both created an origin of rational metaphysics and has been direct been an inspiration to philosophical construction in following centuries.