what he perceives and does not know, with what he knows, or what he knows
and perceives with what he knows and perceives.

Theaetetus is unable to follow these distinctions; which Socrates proceeds
to illustrate by examples, first of all remarking, that knowledge may exist
without perception, and perception without knowledge. I may know Theodorus
and Theaetetus and not see them; I may see them, and not know them. 'That
I understand.' But I could not mistake one for the other if I knew you
both, and had no perception of either; or if I knew one only, and perceived
neither; or if I knew and perceived neither, or in any other of the
excluded cases. The only possibility of error is: 1st, when knowing you
and Theodorus, and having the impression of both of you on the waxen block,
I, seeing you both imperfectly and at a distance, put the foot in the wrong
shoe--that is to say, put the seal or stamp on the wrong object: or 2ndly,
when knowing both of you I only see one; or when, seeing and knowing you
both, I fail to identify the impression and the object. But there could be
no error when perception and knowledge correspond.

The waxen block in the heart of a man's soul, as I may say in the words of
Homer, who played upon the words ker and keros, may be smooth and deep, and
large enough, and then the signs are clearly marked and lasting, and do not
get confused. But in the 'hairy heart,' as the all-wise poet sings, when
the wax is muddy or hard or moist, there is a corresponding confusion and
want of retentiveness; in the muddy and impure there is indistinctness, and
still more in the hard, for there the impressions have no depth of wax, and
in the moist they are too soon effaced. Yet greater is the indistinctness
when they are all jolted together in a little soul, which is narrow and has
no room. These are the sort of natures which have false opinion; from
stupidity they see and hear and think amiss; and this is falsehood and
ignorance. Error, then, is a confusion of thought and sense.