 Protagoras’ aim is not merely to abolish the idea of truth which is shattered into an endless number of private truths; his aim is to replace this criterion with another, more effective criterion, that of the useful. It is by reflecting on the issue of the useful that the sophist, while respecting everybody’s opinion, shows his wisdom. The useful varies from one situation to the next, and the problem is to identify what is truly expedient in each case.