each individual. Plato ascribes relativism to Protagoras and uses his character Socrates as a foil for his own commitment to objective and transcendent realities and values. Plato ascribes to Protagoras an early form of what John Wild categorized as phenomenalism. That being an assertion that something that is, or appears for a single individual, is true or real for that individual. However, as described in Plato's Theaetetus, Protagoras's views allow that some views may result from an ill body or mind. He stressed that although all views may appear equally true, and perhaps, should be equally respected, they certainly are not of equal gravity. One view may be useful and advantageous to the person who has it, while the perception of another may prove harmful. Hence, Protagoras believed that the sophist was there to teach the student how to discriminate between them, i.e., to teach virtue. Both Plato and Aristotle argue against some of Protagoras's claims regarding relativity; however, they argue that the concept provides Protagoras with too convenient an exemption from his own theory and that relativism is true for him yet false for those who do not believe it. They claim that by asserting that truth is relative, Protagoras then could say that whatever further theory he proposed must be true. Agnosticism Protagoras was a proponent of either agnosticism or, as Tim Whitmarsh claims, atheism, on the grounds that since he held that if something is not able to be known it does not exist. Reportedly, in Protagoras's lost work, On the Gods, he wrote: "Concerning the gods, I have no means of knowing whether they exist or not, nor of what sort they may be, because of the obscurity of the subject, and the brevity of human life." According to Diogenes Laërtius, the outspoken, agnostic position taken by Protagoras aroused anger, causing the Athenians to expel him from the city, and all copies of his book were collected and burned in the marketplace. The deliberate destruction of his works also is mentioned by Cicero. The classicist John Burnet doubts this account, however, as both Diogenes Laërtius and Cicero wrote hundreds of years later and as no such persecution of Protagoras is mentioned by contemporaries who make extensive references to this philosopher. Burnet notes that even if some copies of the Protagoras books were burned, enough of them survived to be known and discussed in the following century.