Quine selects the scope of prediction and test of research in. In ' evidence' chapter he says that the forming of the critical systems starts with the stimulus of the senses, which gives us, the observation sentences. The observation categoricals are deduced from them. Tests are on the basis of these categoricals. He says he does not believe in the Cartesian scientific certainty, and then mentions his' theory of naturalized Epistemology' as an alternative way