 Most of those generally recognized as “wise men” (sophoi) and “students of nature” (physikoi) who appeared in this milieu, thought within the same broad terms as the poets and orators. Justice was widely, if not universally, treated as a fundamental constituent of cosmic order. Some of the physikoi influenced political life, notably a number of the Pythagoreans in southern Italy. Others held themselves aloof from political action while still identifying commonalities or consonances between nature and politics, for example, Democritus of Abdera, whose atomist philosophy comported with a defense of political life, and so of the justice that it required individuals to enact, as being necessary for individual flourishing (see e.g. Democritus’ fragment DK B252 = Taylor D116). However, these portraits of broad consonance between nature and politics were challenged in the mid to late fifth century BCE by some among a new breed of thinker and actor, the professional teachers (“sophists”), who began to ask whether the laws and customs (nomos, singular; nomoi, plural) embodying political justice were truly a reflection of justice in nature (phusis), or merely an imposition of arbitrary human norms. Most of the sophists argued the latter, though they did so along a spectrum of interpretation (for which our evidence rests heavily on Plato, who portrays Socrates arguing with a considerable number of sophists): for Protagoras (an itinerant teacher from Abdera who is depicted in Plato’s Protagoras and Theaetetus), the human creation of political life was a cause of celebrating human virtues and practical abilities; for Thrasymachus (an ambassador to Athens from Chalcedon, a city in Asia Minor near modern Istanbul, who is depicted in Plato’s Republic), it was a cause of condemnation, the powerful in any city imposing laws to serve their own advantage. This nomos-phusis debate raised a fundamental challenge to the governing intellectual assumptions of the polis, even though the sophists advertised themselves as teaching skills for success within it, a number of them being employed as diplomats by cities eager to exploit their rhetorical abilities. Socrates and Plato would respond to this challenge in shaping a new genre of “philosophy” which broke the mould of their predecessors (on the genre of philosophy, see Nightingale 1993a). While it is broadly true to say that Greek political thinkers generally presupposed the importance of justice, in the fifth and fourth centuries BCE many of them also increasingly problematized it.