The famous Greek historian Ksenophanes says: Anyone wanting, against money they sell wisdom.. the most important representatives
Protagoras, Gorgias, Prodikos, Hippias, Antiphon, Thrasymakhos and Kallikles.
They are not representatives of a philosophy school. they are the natural end result of the change of social conditions in practical work, the road has become a necessity is a traveling teacher who teaches money.