Tell, Håkan. 2011. Plato's Counterfeit Sophists. Hellenic Studies Series 44. Washington, DC: Center for Hellenic Studies. http://nrs.harvard.edu/urn-3:hul.ebook:CHS_Tell.Platos_Counterfeit_Sophists.2011.
4. Itinerant Sophoi
It is also reported that he was sent as an ambassador by his own city to Athens in 427 BCE to ask for their assistance, since the people of Leontini were involved in a war with the Syracusans.  This was supposedly his first trip to Athens, and he is said to have been already sixty years old.  He gave a public performance in the theater of the Athenians apart from the funeral oration mentioned above, and there is also a story about him performing together with Hippias in purple clothes.  He taught in Argos, where he was so hated that his students had to pay fines, and he was active as a teacher in Boeotia and in Thessaly.  Isocrates, finally, mentions that he failed to inhabit any one city steadily. 
In the Hippias Minor, Hippias says that:
Plato mentions that Hippias visited Olympia wearing clothes all of which he had made for himself: ring, skin-scraper, oil-flask, sandals, cloak, tunic, and girdle, and that, besides this, he had with him poems, epics, tragedies, dithyrambs, and many prose writings.  He is also said to have published a List of Olympic Victors.  When asked by Socrates what he was teaching in Sparta, he answers that they very much enjoy hearing:
Finally, Xenophon mentions a discussion between Socrates and Hippias, who he says had arrived in Athens after a long absence. 
In order to appreciate better how the sophists could travel the Greek world and why they were held in such high regard as teachers, we shall survey our primary material for historical predecessors. We shall be on the lookout for itinerant sophoi who exhibited similar educational expertise as the sophists.
Diogenes also tells us in the same place that he went to Crete before going back to Samos only to leave again for Croton. Isocrates (Busiris 28), too, attests to Pythagoras’ pursuit of wisdom through his travels. He writes that Pythagoras went to Egypt and became a disciple of the Egyptians (μαθητής). Herodotus (2.81) also links Pythagoras with Egyptian religious practices and seems to have him in mind in a similar reference in 2.123. 
Democritus mentions a visit to Athens in fragment 116 and talks about living abroad in fragment 246. Diogenes Laertius narrates that his father entertained king Xerxes, and that he in return left Magi and Chaldaeans behind to instruct the young Democritus.  We also hear that he went to Egypt and was instructed by priests, that he visited the Chaldaeans in Persia, and that he made it to the Red Sea. Some also add that he went to India as well as to Ethiopia. 
This encounter has been questioned on chronological grounds.  What interests me, however, is less the historicity of the meeting than Herodotus’ conceptualization of the encounter. Solon travels from Athens to Sardis and is received by Croesus because of his reputation for wisdom—he is one of the Seven Sages—to validate Croesus’ claims to happiness (εὐδαιμονία). Croesus’ reception of Solon invokes the framework of guest-friendship (ξενία): it is as his guest-friend that Croesus receives and entertains Solon at his court in Sardis and it is in this capacity that he asks him to assess his fortunes. In the Herodotean narrative, then, Solon’s travel to and reception by Croesus are predicated on and mediated through the cultural networks provided by ξενία. Is the prominence of ξενία limited to this encounter in Herodotus, or can we find this association between ξενία and σοφία even in the material on the Presocratics and sophists? We shall attempt to address these questions next.
Ξενία and Σοφία
I suggest that early sophoi conducted much of their travel within the network of xenia, and that the sophists were simply continuing a longstanding practice that had considerable historical resonance. 
Rosalind Thomas has also considered the role of traveling sophoi. She outlines the intellectual milieu in which Herodotus participated and against which she believes his work should be understood; and she paints a picture of extensive intellectual travel in the fifth century:
It seems safe to conclude that travel was extremely important for practitioners of wisdom in the fifth century. But what do we know about the situation in the archaic period? Montiglio has conducted a broader exploration of the link between travel and philosophy, and she emphasizes the importance of travel for wise men from Odysseus onward. Montiglio highlights what an undesirable and anomalous activity travel was in the Greek world: it is often connected with suffering, supplication, and exile in epic and tragedy, and when associated with trade it is often represented as a great evil.  Within such cultural attitudes, Montiglio distinguishes between two types of travel, one positive and one negative. The positive one is linked with knowledge, embraced by the example of Odysseus, who “learns from his toilsome wanderings.”  Later Solon came to personify this link between travel and learning, so much so that he “inaugurates a tradition which eventually spreads so widely that Diogenes Laertius regards the philosopher who loathes travelling as an exception.” This “love of knowledge” that Solon’s travels represent, in the words of Montiglio, “is the motive that drove several other Presocratics to travel extensively.” She continues:
The other form of travel is motivated by the need to work and earn money, and here we find the sophists.  This type of travel is modeled on the merchant, where need or greed motivates travel, and, in the case of the sophists, teaching and money-making—not desire to see the world and learn, as with the Presocratics—are given as the determining factors for them going from city to city. But in establishing these models and in seeking to reconstruct the cultural attitudes associated with them, Montiglio relies heavily on the judgment of Plato. She thus concludes—just as Plato did—that the sophists had no philosophical ambitions, that they only traveled to make money, and that they were generally despised in the Greek world. 
The origin of these structural homologies can be found neither by looking exclusively at outside influences nor at endogenous developments, but by analyzing “the interaction between the polities—the peer polity interactions.” The corollary of this statement is that no single place can be pinpointed as the origin of a particular cultural form. Rather, “the different communities developed simultaneously and their structural homologies developed with them.”
On the regional level, the Panhellenic sites played an important part in furthering contacts between polities, and we will explore this in the next chapter. But the most pervasive and multidimensional network to promote communication and interaction is the xenia network outlined above.  Through this network, we see precisely the preoccupation with competition, emulation, and exchanges that pertain to a cultural framework shared by a larger group of autonomous poleis. But who where the dominant players participating in these exchanges? When addressing this issue, Renfrew and Cherry downplay the importance of traders, saying instead that the “travels of the decision-makers may have been more important, some undertaken, no doubt, in the course of arranging marriage alliances, or simply in gift-exchange.”  The locus of interest is thus on interactions between the decision-makers in the various social units. But this raises the question of how, where, and under what circumstances they met. It becomes especially important if we are to attribute to this type of interaction the shaping and influencing of the social structures of the participating communities. Renfrew and Cherry do not explore these aspects of their theory. Instead they point out that this kind of research is in need of further pursuit, the lack of which they deplore:
Let us pause for a moment to recapitulate the main points of the argument thus far. We have assessed the importance of travel for the sophists and linked it to the general theme of travel by other sophoi. Rather than assuming the Platonic bias and distinguishing between the Presocratics who traveled for knowledge and the sophists who traveled for pay, it seems reasonable to assume that the same motivations that induced early sophoi to travel were still at play in the time of the sophists. We have further suggested that it was within the framework of xenia that much of the philosophical travel occurred. By drawing on the peer polity interaction model, we have called attention to the importance of the inter-polis interaction engaged in by decision-makers and the flow of information resulting from their interactions. Here xenia becomes crucial in understanding how interactions between the elites in the various communities took place. In the remainder of this chapter, I will try to map out how all of this played out in the time of the sophists. We shall explore what role the xenia system had in their travels, and we will also try to push the question of historical predecessors in the direction of the Seven Sages.
Ξενία in the Time of the Sophists
In this passage, we find the same language as in Herodotus’ narrative on Croesus and Solon, that is, the language of xenia and gift-exchange. It places Protagoras in a similar relationship to Xerxes as Solon to Croesus. Note Philostratus’ emphasis on the wealth of Protagoras’ father (πλούτῳ κατεσκευασμένος), a prerequisite for acts of xenia. In the Protagoras (316c7) we hear that the sophist’s audience are the best young men (οἱ βέλτιστοι τῶν νέων), and here βέλτιστοι is a class marker to indicate the young men’s social standing as aristocrats. 
Ξενία and the Seven Sages