  The empiricist conception of knowledge that Theaetetus unwittingly brings forth, and which Socrates is scrutinising, takes the objects of thought to be simple mental images which are either straightforwardly available to be thought about, or straightforwardly absent. The First Puzzle showed that there is a general problem for the empiricist about explaining how such images can be confused with each other, or indeed semantically conjoined in any way at all. The Second Puzzle showed that, because the empiricist lacks clear alternatives other than that someone should have a mental image or lack it, he is wide open to the sophistical argument which identifies believing with having a mental image, and then identifies believing what is with having a mental image, too—and so “proves” the impossibility of false belief. The Third Puzzle restricts itself (at least up to 190d7) to someone who has the requisite mental images, and adds the suggestion that he manages to confuse them by a piece of inadvertency. Socrates’ rejoinder is that nothing has been done to show how there can be inadvertent confusions of things that are as simple and unstructured, and as simply grasped or not grasped, as the empiricist takes mental images to be. Just as speech is explicit outer dialogue, so thought is explicit inner dialogue. What the empiricist needs to do to show the possibility of such a confusion is to explain how, on his principles, either speech or thought can fail to be fully explicit and fully “in touch” with its objects, if it is “in touch” with them at all.