Pros And Cons Of Protagorean Relativism

Protagorean Relativism is generally considered self-refuting. It is noticeable that the measure doctrine: “man is the measure of all things, of what is that it is, and of what is not that is not” (Tht. 152a2-4) suggests that there are only relative truths for everyone but no objective truth; however, it insists that the above statement is an objective truth. That is to say, while Protagoras claims that truth is relative to each person, rejecting the possibility of error (Lee, 2005:33), he tries to universalise his doctrine as a superior absolute truth to the audience and forces them to believe, thus is self-refuting.
But new problem shows up. Critics from George Grote to Gregory Vlastos protested at the way Plato drops the relativizing qualifiers