In the paper the author considers the problem of solubility of philosophical questions. He tries to substantiate thesis that rational philosophical reflection can allow us to choose between some opposite philosophical hypotheses. In this meaning he accepts philosophy as a positive knowledge. To support this point of view he gives some examples of philosophical theories, which - in his opinion - are prescribed (finitism, apriorism, sensualism and others). He analyses relationship between philosophical knowledge, science and common sense as well.