When a simple man who has no skill in dialectics believes an argument to be true which he afterwards imagines to be false, whether really false or not, and then another and another, he no longer has any faith left, and great disputers, as you know, come to think, at last that they have grown to be the wisest of mankind; for they alone perceive the utter unsoundness and instability of all arguments, or, indeed, of all things, which like the currents in the Euripus, are going up and down in never-ceasing ebb and flow.