From the Beginning to Plato

352 PLATO: METAPHYSICS AND EPISTEMOLOGY
and C. And if A, B and C are known by knowing their definitions, the same
problem recurs. Either there is an infinite regress and knowledge does not exist,
or some kind of knowledge does not involve an account—a definition—of the
thing known. This last seems to be the sort of knowledge needed of the
Republic’s unhypothesized beginning, but Plato never clarifies what kind of
knowledge it could be.
Although the final argument against the dream theory seems to show that
knowledge does not need an account, Plato proceeds to consider different
interpretations of ‘account’. The serious suggestions—and it is important to bear
in mind that the item known is an object—are that knowledge of X requires (1)
the ability to analyse X into its elements or (2) the ability to give a mark
distinguishing X from everything else. 63
Against (1) Socrates objects that a person might correctly judge that the first
syllable of ‘Theodoras’ contains ‘t’ ‘h’ and ‘e’, but on another occasion, when
writing the name of Theaetetus, incorrectly judge that that same syllable contains
the elements ‘t’ and ‘e’. Then he did not know the syllable ‘t-h-e’ the first time
even though he correctly analysed it into its elements. Knowledge is infallible.
Against (2) Socrates objects that the ability to give a distinguishing mark of X
is presupposed in having a true judgement about X: otherwise one would not have
a true judgement about X to begin with. So (2) adds nothing to the idea of having
a true judgement about X. 64
With this the discussion comes to an end. One puzzle is the question of why
Plato neglects the notion of giving an account which he himself uses in other
dialogues when discussing knowledge. If being able to give an account includes
the abilities to explain why something is so and to defend the claim in question,
then some of the Theaetetus’ difficulties are overcome.
Another problem arises from the dialogue’s use of sensible objects as objects
of knowledge. Does Plato now countenance knowledge of the sensible world, or
is the negative conclusion of the dialogue rather meant to reinforce the lesson that
we cannot explain the nature of knowledge when its objects are disregarded?
It seems the Theaetetus cannot be intended as a demonstration that an account
of knowledge must fail if it does not bring in Forms as the object of knowledge,
for if that were Plato’s aim the neglect of his own interpretation of ‘account’
would only too obviously undermine his argument. And we’ve already seen that
some objections against the proposal that knowledge be defined in terms of
judgement apply equally well when its objects are taken to be Forms. For
example, accounts of Forms are as vulnerable to the epistemological regress as
accounts of anything else. 65
None of the objections against proposed definitions of knowledge turn on the
objects used in the examples not being of the right kind. The one firm conclusion
of the dialogue is about the sort of state knowledge is, not the nature of its
object: knowledge must be sought in judgement rather than perception (187a).
Despite this conclusion—which could be supposed to be undermined by the rest
of the dialogue—one might still see the Theaetetus as reinforcing Plato’s view