What is the source of knowledge? What can we know? Questions like these dominated Western philosophy throughout the 17th and 18th centuries. This philosophical period was known as the epistemological turn. The search for the source of knowledge was not easy. This question had led to many disagreements about the nature of knowledge, and a philosophical war was waged that would last two centuries. It all started in the 17th century with a French philosopher named René Descartes. The answer to his epistemological quest was rationalism. For Descartes, rationalism was the key to keeping our reality under control. Descartes had undergone a process of eliminating everything he thought he knew to find the only source of knowledge. After much examination Descartes came to the conclusion that there were few things that could be considered pure knowledge. Because most of the things we know come from the senses, and the senses were fallible. He made a crucial discovery that would change the face of philosophy forever. The mind he considers is the instrument that can lead to a pure source of knowledge unbridled by the senses. He believed that we can only trust our mind with what we can intuit or “deduce” on our own. Descartes called these ideas a priori knowledge. A priori are ideas that are innate and that we can only arrive at through a special type of reasoning known as deductive reasoning. Descartes famously states the statement “cogito ergo sum” to answer the question of our existence. Because if the senses deceive who can say that the world we live in is a lie created by an evil genius we call god.” Descartes believed that if he existed it was because his mind was engaged in the thought process. In other words only... half a paper... around, and empiricists and rationalists have managed to build and destroy certain views in ways that make my head spin, but Kant's view will always fascinate me. Not only because it builds a world of which we are not the center and reduces reality to mental conceptions. It makes us reflect on this world of impossibilities. He realizes that as human beings we desire to know, believe, and seek answers to an infinite amount of possibilities, and there is a lot of truth in this. We still seek and ask questions that are not easy to answer because our reason pushes us to do so. As Kant once said: “Human reason has this peculiar fate of being burdened in a kind of its knowledge by questions which, as prescribed by the very nature of reason itself, it cannot ignore, but which, transcending all its powers also not I can answer.