Such argumentation is proper, sophists maintained, because there are no absolute standards in truth, morality, or law. In the words of one anonymous sophist, in the Dissoi Logoi or "Opposing Arguments," moral values are relative to any particular moment: 
Two-fold arguments are put forward in Greece by those who philosophize. Some say that the good is one thing and the bad another, but others say that they are the same, and that a thing might be good for some persons but bad for others, or at one time good and another time bad for the same person. I myself side with those who hold the latter opinion. 
For those who accepted these views, all standards and all conclusions were left without anchor, as floating products of whim. Having rejected divine inspiration as the source of such standards, they took the first steps toward skepticism: the idea that there is no knowledge, only opinion, and that an idea is true only in relation to a person who accepts it. Aristotle described the views of the sophist Protagoras in this way: 
Protagoras said that man is the measure of all things, meaning that what appears to each person also is positively the case. But once this is taken to be so, the same thing turns out both to be and not to be, and to be bad as well as good, not to mention other opposites, since often what seems noble to this group of people will seem opposite to that group, and since what appears to each man is taken to be the measure.
According to Protagoras as he is portrayed in Plato's work, these moral views are based on a dichotomy between experience and being, which requires the manipulation of appearances as a means to establish validity: "But the man whom I call wise is the man who can change appearances-the man who in any case where bad things both appear and are for one of us, works a change and makes good things appear and be for him." 
These are the kinds of ideas that gained prevalence in Athens during the war with Sparta. The orator's job -and the specialty of the sophists - was the ability to change appearances in order to win an argument. In his play The Clouds, a biting satire directed at such teachings, the Athenian comic playwright Aristophanes dramatized the sophistic method of arguing with his allegorical characters "Good Argument" and "Bad Argument." Bad Argument can prevail over Good Argument by slippery forms of persuasion that can make the worse case look better, and thus allow the bad to triumph over the better.43 In his Rhetoric, Aristotle attributed such argumentation to Protagoras, and noted many critical objections to the training the sophist had offered. 

In the sophists' view, social, political, and legal principles, which most Greeks understood to be aspects of ethical thought, are arbitrary human constructs that cannot be derived from the facts of nature. Because the sophists could not find immutable moral standards in nature ( phusis), many decided that such standards were a mere convention (nomos). Given this view, there is no way to judge the truth of an argument, only its effectiveness, and a method of reasoning will be judged as appropriate if it is convincing. Such views were strengthened and complicated by an influx of philosophical ideas into fifth-century Athens. Archelaus, for instance-the earliest philosopher of whom we know in Athens -merged early physical theories with social theories, in an attempt t