Taylor, C. C. W., and Mi-Kyoung Lee. "The Sophists." (STANFORD ENCYCLOPEDIA OF PHILOSOPHY).

The Greek word sophistēs, formed from the noun sophia, ‘wisdom’ or ‘learning’,has the general sense ‘one who exercises wisdom or learning’. As sophia could designate specific types of expertise as well as general sagacity in the conduct of life and the higher kinds of insight associated with seers and poets, the word originally meant ‘sage’ or ‘expert’. In the course of the fifth century BCE the term, while retaining its original unspecific sense, came in addition to be applied specifically to a new type of intellectuals, professional educators who toured the Greek world offering instruction in a wide range of subjects, with particular emphasis on skill in public speaking and the successful conduct of life. The emergence of this new profession, which was an extension to new areas of the tradition of the itinerant rhapsode (reciter of poems, especially of Homer), was a response to various social, economic, political and cultural developments of the period. The increasing wealth and intellectual sophistication of Greek cities, especially Athens, created a demand for higher education beyond the traditional basic grounding in literacy, arithmetic, music and physical training. To some extent this involved the popularization of Ionian speculation about the physical world (see Presocratic Philosophy), which was extended into areas such as history, geography and the origins of civilization. The increase in participatory democracy, especially in Athens, led to a demand for success in political and forensic oratory, and hence to the development of specialized techniques of persuasion and argument. Finally, the period saw the flourishing of a challenging, rationalistic climate of thought on questions including those of morality, religion and political conduct, to which the sophists both responded and contributed. It is important to emphasize the individualistic character of the sophistic profession; its practitioners belonged to no organization, shared no common body of beliefs and founded no schools, either in the sense of academic institutions or in that of bodies of individuals committed to the promulgation of specific doctrines. In what follows we shall illustrate the diversity of sophistic activities, while considering the extent to which we can nevertheless identify common themes and attitudes. . . .

http://plato.stanford.edu/entries/sophists/