In optics a knowledge of conic sections is required for the construction of lenses. Moreover, he believed that this new method of acquiring knowledge could be extended to biology and would improve human life through technological applications. This method will be based on the procedures developed in the Geometry. There is nothing about which there is not some dispute - and thus nothing that is not doubtful. His conclusion is that he should rely on his own reason in the search for knowledge.
Geometry requires the use of figures so that it utilizes the imagination instead of the reason.
Considering them individually he will treat them as relations between lines, that is, geometrically. This is starting with the simplest objects. Considering the relations together, he will use symbols, treating them algebraically. His method is a way of discovering truths which are both certain and exact. He refers to them as clear and distinct ideas.