We are living in a world where there are various theories, views and opinions about many different issues. These theories, views and opinions are changing, as everyday new scientific discoveries are made and new theories conducted. Consequently, our knowledge and what we know for certain, or in other words what we think that we know for certain today might change tomorrow. This raises the question whether there is anything certain and what we can know with certainty. Some philosophers have searched for the answer of this question. Descartes and Hume are among them who are concerned with the problem of certainty. Both Descartes and Hume have tried to find a basis for certain knowledge. However, they differ from each other in their point of view on the foundation of this certain knowledge.
             Descartes' aim is to find out a system of thought, which will be the foundation of the principles of absolute certainty. Descartes starts with rejecting any idea as certain and he tries to discover the basis of certainty. Descartes uses the method of doubting in order to find principles, which cannot be doubted. He starts doubting every item of knowledge he previously believed in order to arrive at certain knowledge, the " first principle" which is fundamental, unconditionally necessary, true and indubitable. His purpose is to find indubitable truth and build up his knowledge on this certain truth. By this method of doubt, Descartes shows how uncertain our knowledge is even it seems most obvious to us. Descartes starts doubting from his own experience. First type of experience he looks for is sense perceptions. As a result of doubting, Descartes finds out that our senses can deceive us and they are not reliable because they can be imaginary, illusionary and deceptive. To illustrate, he gives the example of a wax melted by fire. After melting, the color, size and shape of the wax changes. This means our sense perception about wax cha...