Dualism is a broad term that can encompass many areas within philosophy itself. In aspect to metaphysics, it classifies the types of entities in the world into two subcategories, physical and non-physical substance. While this may seem like a very broad and ambiguous opinion, it becomes very specific regarding our very existence. Paul Churchland lays this out very explicitly in his book Matter and Consciousness and defines dualism as the idea that “the essential nature of conscious intelligence lies in something non-physical” (Churchland 1). Although dualism is a highly regarded and popular view on the state of existence, its main arguments present a number of problems that detract from the credibility of its reality. René Descartes, who has often been called the father of Western philosophy (Wikipedia Descartes), entered the scene in Europe in the 17th century. Galileo's imprisonment and the Church's monopoly on knowledge had put a damper on scientific learning across Europe. This, combined with Aristotle's outdated theories that held much weight in science and philosophies, had spread a growing sense of skepticism throughout the world. Descartes' Meditations were the first real response to this dangerous approach. He began by embracing the idea of ​​skepticism that all his ideas about the world must be shaken and then attempted to build a model from scratch. Through the series of Meditations he reaches a critical point which, in his opinion, cannot be refuted and from that point he begins to shape his idea of ​​the world. This point is one of the most cited phrases in philosophy, “Cogito ergo sum”, that is, “I think therefore I am” (Descartes' Mediation 2). He states that they were... half the documents......about objections and responses. Oxford: Oxford UP, 2008. Print.3- "Dissociative identity disorder (multiple personality disorder): signs, symptoms, treatment." WebMD. WebMD. Web. 14 March 2012. http://www.webmd.com/mental -health/dissociative-identity-disorder-multiple-personality-disorder4- “Elementary particles < http://abyss.uoregon.edu/~js/21st_century_science /lectures/lec16.html>5- Hofstadter, Douglas R., Daniel Clement. Dennett and Raymond Smullyan. The Ego of the Mind: Fantasies and Reflections on Self and Soul New York: Basic, 1981, Chapter 23 “The Unfortunate Dualist.”6- “On Lockean Dualism”7- “Problems from Philosophy.” 8- “Renato Descartes”