  The peritropê (“table-turning”) objection (171a–b) is this. Suppose I believe, as Protagoras does, that “All beliefs are true,” but also admit that “There is a belief that ‘Not all beliefs are true’.” If all beliefs are true, the belief that “Not all beliefs are true” must be true too. But if that belief is true, then by disquotation, not all beliefs are true.  So I refute myself by contradicting myself; and the same holds for Protagoras.