 Protagoras’ teaching had a practical and concrete goal, and many of the surviving testimonies and fragments suggest that it was mainly devoted to the development of argumentative techniques (which were probably investigated in texts such as the already mentioned Antilogiai and The Art of Eristics). Unfortunately, we have little evidence of what these actually were. In all probability, assertions such as that on every matter there are two logoi opposed to one another (80A1, B6a DK) or that it is impossible to contradict (80A19 DK), along with the claim to make the weaker logos (the) stronger (80B6b DK), belong to this context. Part of his teaching was also devoted to grammatical or linguistic issues and poetry analysis. More in general, it is also unclear the relation between his teachings and the apparent relativism of his famous thesis that the man is the measure of all things. Ancient sources report that this sentence opened Truth, a public declamation (epideixis) with which he presented himself to the public to potential pupils.