In Metaphysics Γ 4-6 Aristotle argues that Protagoras is committed not just to denying the PNC, but also to asserting its contrary. In this paper, I offer an analysis of this commitment. I try to show that Aristotle is working with a specific idea in mind: a Protagoreanism ontologically linked to the flux doctrine, as Plato suggested in Theaetetus 152-160.

The account of knowledge in Plato’s Theaetetus, as true belief meta logou, seems to lead to a regress, which may be avoided by defining one kind of knowledge as true belief that rests on a different kind of knowledge. I explore a specific version of this move: to define knowledge as true belief that results from a successful and proper exercise of a rational capacity (a dunamis meta logou).

In this paper I explore a famous part of Plato’s Theaetetus where Socrates develops various models of the mind (picturing it first as a wax tablet and then as an aviary full of specimen birds). These are to solve some puzzles about how it is possible to make a mistake. On my interpretation, defended here, the discussion of mistakes is no digression, but is part of the refutation of Theaetetus’s thesis that knowledge is “true doxa”. It reveals that false doxa (...) is possible only if there is a certain stock of abstract knowledge, conceptual knowledge, that is not awareness of the particular individual that is being described. The individual must be identified under some description, or seen as something of a certain kind. Error can only occur if the description applied misdescribes the situation, but then if it is to be applied falsely it must first have been known from somewhere else. So knowledge cannot be reduced to the application of descriptions to particulars, but is to be found in the prior possession of abstract descriptions that can be deployed in identifying particular individuals on the ground. (shrink)

Two readings of the much-discussed περιτροπή argument of "Theaetetus" 170c-171c have dominated the literature. One I call "the relativity reading". On this reading, the argument fails by ignoratio elenchi because it "carelessly" omits "the qualifications 'true for so-and-so' which [Protagoras'] theory insists on" (Bostock 1988: 90). The other reading I call "the many-worlds interpretation". On this view, Plato's argument succeeds in showing that "Protagoras' position becomes utterly self-contradictory" because "he claims that everyone lives in his own relativistic world, yet at (...) the same time he is forced by that very claim to admit that no one does" (Burnyeat 1976b: 48). I discuss and criticise both readings, and present a third, according to which the point of the argument is, very roughly, that Protagoras is committed to equating truth and truth-for, and so, further, to their intersubstitutability. This further commitment proves fatal to his argument. (shrink)

With the use of a particular metaphor, which appears at the end of the Cratylus and is taken up with perfect symmetry at the beginning of the Theaetetus, Plato certainly wanted to indicate the succession of Cratylus–Theaetetus as an order for reading the two dialogues, which Trasillus faithfully reproduced in structuring the second tetralogy of Platonic dialogues. The claim of the theory of ideas, with which the Cratylus ends, must therefore be considered the background in which to place not only (...) the analysis of the name carried out in the Cratylus, but also the discussion and criticism of the epistemological theories examined and refuted in the Theaetetus. The transition from the discussion of the name to that of the logos is another important theoretical element that connects the two dialogues. Another one is the theory of knowledge, already precisely elaborated in the Cratylus, and taken up and deepened in the Theaetetus. Finally, the theme of false and error is a third theoretical element common to the two dialogues, which, starting from Euthydemus, finds its solution in the Sophist. (shrink)