In the long development of philosophy, skepticism contains its own significance. The basic spirit of skepticism refers to its negation of the foundation of knowledge, but this spirit makes skepticism somehow relevant to problems of metaphysics, epistemology and ethics. In metaphysics，skepticism holds the position that we will never be able to know anything whatsoever. In epistemology, skepticism can always raise arguments refuting the justification of any sort of knowledge. In ethics, the most prominent function of skepticism is the fact that all truth claims are not assured to forge an evaluative position. Therefore, with regard to the three major domains of philosophy, skepticism since the very beginning of philosophy plays the role of subverting knowledge with the purpose of stressing the fact that knowledge is an endless process of epistemic pursuit.
For this reason, history plays a role of crucial importance in skepticism. We an see from the debates between Socrates and sophists that skepticism constantly demonstrates its value by being nominated in different names. In the Hellenistic era, skepticism is represented under the title Pyrrhonism which can be further divided by schools represented by Aenesidemus and that of Sextus Empiricus. In the era of Middle Age, there is de Montaigne represented skepticism. In the development of modern world, R. Descartes and D. Hume undoubtedly represented the thinking of skepticism. We finally come to the contemporary world of skepticism which is represented by P. Feyerabend’s relativism.