With the new found importance of the epistemological discussions in the new era, studying the epistemological views and ideas of the Sophists as one of the most influential intellectual movements of the Greek’s golden age has become increasingly more important. Although we mostly know the viewpoints of sophists through their prominent opponents, namely Plato and Aristotle, ironically despite this conflict of ideas, the most creditable and valid reports on the mental school of the sophists, has reached us through these same opponents. This paper aims to study the critical aspects of the Sophists’ ideas from Plato’s viewpoint as evident in his writings, especially his Protagoras, while presenting relevant viewpoints of famous sophists on episteme. By expanding Heraclitus and Parmenides’s skeptical view points as well as the transmission of the object of knowledge from nature to human, they have essentially reduced episteme to sensory perceptions and furthermore, to the “individual” range and being subjected to being self-refuted. To confront this idea, Plato, through critical analysis of the relativism that emerged from the sophists’ “impressionism”, demonstrated the possibility of acquiring true knowledge and, through that, saving religious and moral values and beliefs. This effort would perhaps allow us to regard Plato’s philosophical doctrine including the creation of “Idea” as a reaction to the epistemological teachings of the sophists.