Dr. Sproul takes the time to repeat the four principles from the previous lecture and look at each one in greater detail. The first is that it is an illusion, the second one is that it is self-created, the third is that it is self-existent, and the fourth is that it was created by something ultimately that is self-existent. In “The Illusion of Descartes”, Dr. Sproul introduces René Descartes, the father of modern rationalism and shows how Descartes’ inquires explain and correlate to using the process of elimination on the four principles.