From the Beginning to Plato

FROM THE BEGINNING TO PLATO 351
because Plato is often, mistakenly, taken to be marking an important contrast
between the objects of perception and judgement. 62 He first distinguishes the
subject of perception from the senses through which the subject—the soul—
perceives colour, sound, etc. A single subject is aware of the different kinds of
sense object and observes relations between them.
Further, anything perceived through one sense cannot be perceived through a
different sense. For example, I cannot hear a colour. So if anything is common to
different kinds of sensible object, the soul cannot ‘grasp’ it by perception.
Now, ‘being’ is a common notion applicable to different kinds of sensible
object: both a sound and a colour are. So the soul grasps ‘being’ not through a
sense but on its own.
But to know is to know the truth, and knowing the truth is grasping being, i.e.,
awareness of what really exists or is the case. Since perception cannot grasp
being it cannot put us into contact with the truth, and therefore it can never be
knowledge.
Plato’s argument rests on an ambiguity in the notion of ‘grasping being’.
When the common notions are first introduced, to grasp being is to understand
the meaning of ‘being’ or what being is: being itself (not an object like red or a
fact that has being) is not an object of perception but an object of thought.
However, when in the passage’s final argument it is claimed that to attain truth
one must grasp being, the claim has plausibility only if grasping being is
equivalent to grasping an object that really exists or a fact that is the case. And
perception’s inability to grasp what being itself is provides no reason to believe
that perception cannot make us aware of what really exists. On the contrary,
Plato himself affirms shortly afterwards (188e–189a) that if one perceives x, then
x exists.
(2) The definition of knowledge as true judgement is quickly dismissed: true
judgement can turn out to be true by luck, and then it is not knowledge.
(3) The final definition meets this point by suggesting that knowledge is true
judgement ‘with an account’. But the notion of an account is unclear, and
Socrates attempts to explain it in terms of a metaphysical theory he heard in a
dream. The theory says there are simples and complexes. There is no account of
the simples which can only be named and so are unknowable. Complexes are
knowable and expressible in an account which is a weaving together of names.
Even at this abstract level the dream theory faces two objections. First, a
complex either is or is not identical with its elements. If it is, then since its
elements are unknowable, it is unknowable too. If it is not, then it does not have
the elements as parts, and, since nothing else could be part of the complex, it
must be simple and hence (according to the theory) unknowable. Second, if we
consider simples and complexes such as syllables and their letters, the letters are
knowable independently of any account of them.
Both arguments have plausibly been supposed to be meant to apply to the
problem of knowledge of Forms. If a Form F is defined in terms of A, B and C,
the knowledge of F expressed in the definition presupposes knowledge of A, B