The Meditations of First Philosophy is considered one of most important of all of Descartes works. This philosophical study contains Descartes complete metaphysical and epistemological position. He considers the problems of the sources and nature of knowledge; the validity of truth, by questioning everything in sight even those truths that are evident to everyone; the nature and destiny of man; the existence of God, and the creation of the universe. An important issue in his work is that Descartes’ doubt is a practical and rational doubt. That is, the meditator, or the person thinking/arguing, does not just doubt everything at random without any reasons, but is providing solid motives for his/her doubt at each stage. For instance, the author rejects the possibility of being mad, because it would weaken the rationality with which he doubts things. Thus, Descartes is trying to set up his doubts within a rational framework, and in order for his arguments to proceed he needs to stay within those rational borders. Descartes was the first one among philosophers to raise the subject of skepticism. He was the initiator of the claim that we really cannot know with certainty anything about the world around us. The main idea behind this claim is not that these doubts are possible, but that the possibility of the doubts themselves can never be entirely overestimated. From this Descartes point it follows that if people can never be certain about things, then how can we claim to know anything? This skeptical approach was the basis for the new philosophical dogma and became popular with Western people as the ground for their knowledge and understanding of the world. The main problem with this approach however is that no one actually lives skepticism, meaning that no one actually doubts such things as whether other people really exist, or is things are real. On the other hand it has to be taken into consideration that it is difficult to live without skepticism nowadays.

Another important notion brought by Descartes work is the development of a conception of the mind in which the senses and the imagination are mental faculties, rather then spiritual as was argued before him. His claim about people being a thinking creature in the first places provides a better understanding all of his philosophical preferences. Making a concrete distinction between body and soul is one of the major distinguishing points in his work. It give us essential insights into our nature and world and provides with such important conceptions as that of the mind or soul which he says is distinct from the body and thus does not die with the body, but is immortal. This concept in particular is one of the major in religion and for a spiritual person believing in God; it helps us realize with the tools of rational mind the eternal truths of the universe. Its a great work leading us from doubtful thoughts to the more logical and methodically proved understanding of things around us.