Rene Descartes starts his First meditation with the description of false beliefs, which are common for everyone since early years. He writes that in order to build firm basis of scientific knowledge one has to doubt every uncertain belief he has.
             From the very beginning Descartes writes that it's not rational and not objective to trust senses only, as they are likely to be false, moreover being mistaken by sensual assumptions once, it may turn into common practice. Nevertheless, under many conditions sensual perception may be correct, Descartes writes about a number of cases for which such techniques cannot be applied. Descartes writes about a number of conditions, which may influence sensual perception of surrounding world. In general the method he had developed is known as skeptical hypotheses. Descartes uses a certain number of scenarios to prove that sensual perception or empiricism may be false under a number of circumstances. For example he demonstrates how beliefs may be false if he is dreaming, if he is mad or if he is deceived by demons. He writes that in case he is mad he may believe different senseless things (for example that his own head is pumpkin). In case he is dreaming he may believe that he is sitting near a fire, but in reality there would be nothing like this. The same thing would happen if he were deceived by demons, as everything which superpowers show him would have no relation to reality. First meditation shows the premises for fundamental approach to the rational reasoning, which is essential in scientific methods. Descartes formulates his rule that nothing should be believed if it has any obvious uncertainty, in other words he concluded that it's important to avoid including hasty conclusions and prejudices into one's discourses. Descartes says that only pure and firm facts, which cannot be questioned or opposed logically, should form true knowledge or reflect objective reality. Mental activ...