 The puzzle about false belief recurs in the Theaetetus at a crucial juncture in the dialogue’s main argument. Socrates and Theaetetus have rejected the proposal that knowledge is perception and with it the underlying Protagorean view that whatever appears to be the case is the case. Theaetetus’ new proposal, that knowledge is true belief, offers no advance, though, unless they can show that false belief is possible, against sophistic puzzles like we have just seen from the Euthydemus; and while Socrates says he has “often” worried about this, he claims that he is unable to say what false belief is and how it comes about (187b–e). He then develops the worry in much more elaborate ways than before. There is a fuller version of the puzzle than we have seen so far, which explicitly equates believing something “that is not” with not believing anything at all (188d–189b). But Socrates also introduces a distinct, new psychological worry into consideration. If one assumes that false belief by its very nature has a certain structure, namely, of mistaking one thing for another, we must then ask what our cognitive access is to each: do we know each of these, or only one, or neither? (188a–c) Socrates makes this underlying structure explicit when he goes on to analyze false belief as a kind of “other-believing” (allodoxia), where we say in thought that something is one thing instead of another (189c–190e). This analysis avoids the earlier difficulty, since both items can be things that are, and it locates error in our having latched on to the wrong one. From a third-person point of view, this is illuminating, since it exposes precisely why the belief is mistaken. But for just the same reason the description is unacceptable from a first-person point of view for the subject who is taken in: no one, Socrates insists, would ever say to themselves that Socrates is Theaetetus or that one thing is something distinct from it (190a–c). And in fact Plato repeatedly characterizes thinking as saying something to oneself, both in this dialogue (189e–190a) and later in the Sophist (263e–264a); an analogous view also seems to be implicit in the image from Philebus  38e–39a of an internal scribe writing out our beliefs in our soul. This treatment of other-believing in the Theaetetus thus seems to presuppose that both terms must be somehow present to thought in order for the substitution to occur (190d). The possibility that one might have only one of them in the mind, through perception or in some other way, and somehow apply it to the wrong thing in the world is not considered (even though it is something that Plato allows in the case of incorrect names at Cratylus 430a–431b, where he speaks of pointing or otherwise exhibiting the thing while applying a name to it).