Knowledge is the things that one has taken into itself and made the decision to believe that it is true. In order to find absolute certainty about certain pieces of knowledge, Descartes began to ask himself what makes the obtained information true. Thus, Descartes decided to doubt everything until arriving at a concrete truth that could not be denied. This method is called radical doubt. Descartes began to doubt his own existence.
The philosopher asked many questions to himself and even compared dreams to reality. When we dream our senses tell us that we are living the moment and that something is occurring when really is not. Descartes thus poses the possibility of real life being like a dream and that may not be happening. The two deductions of Descartes are that the soul and the body are completely different substances and that the soul is easier to understand than the body. The philosopher explained that God organized the rules of mind-body interaction in such a way as to produce sensations that are generally favorable to the good of the body. Descartes stated that God is the guarantee of the truth of what we know with clarity and distinction, but at the same time, to prove the existence of God, used clarity and distinction. Thus, Descartes attempted to explain the existence of God using an argument that was supposed to be possible only by God. This objection to Descartes’ philosophy is known as the “Cartesian circle”. David Hume was a philosopher who was also in disagreement with Descartes. Hume thought that we do not have, and can not have, any idea of me.
According to Hume, all our ideas are originated in impressions. However, we have no impression that could be at the origin of the idea of self. All that we find when we look at ourselves is a succession of unique perceptions and never a perception of the self. The last idea of Descartes’ philosophy was to prove the existence of the outside world by arguing that the ideas whose cause we attribute to physical objects have the same cause. However, Hume denies that it is possible to prove the existence of the outside world. As Descartes, Hume accepts the distinction between reality and our perceptions, but argues that we only have direct experience of the representations in our mind, not of the physical objects, their supposed causes, and that, therefore, it is not possible to have experience of the causal relation between our mental representations and the objects they are supposed to represent. So there is no reason to think that physical objects are the cause of our perceptions and so, that there are physical objects.