Theaetetus
to be another; for you must not meet me with the verbal quibble that
one--eteron--is other--eteron (both 'one' and 'other' in Greek are
called 'other'--eteron). He who has both the two things in his mind,
cannot misplace them; and he who has only one of them in his mind,
cannot misplace them--on either supposition transplacement is
inconceivable.
But perhaps there may still be a sense in which we can think that
which we do not know to be that which we know: e.g. Theaetetus may know
Socrates, but at a distance he may mistake another person for him. This
process may be conceived by the help of an image. Let us suppose that
every man has in his mind a block of wax of various qualities, the gift
of Memory, the mother of the Muses; and on this he receives the seal or
stamp of those sensations and perceptions which he wishes to remember.
That which he succeeds in stamping is remembered and known by him as
long as the impression lasts; but that, of which the impression is
rubbed out or imperfectly made, is forgotten, and not known. No one can
think one thing to be another, when he has the memorial or seal of both
of these in his soul, and a sensible impression of neither; or when he
knows one and does not know the other, and has no memorial or seal of
the other; or when he knows neither; or when he perceives both, or one
and not the other, or neither; or when he perceives and knows both,
and identifies what he perceives with what he knows (this is still more
impossible); or when he does not know one, and does not know and does
not perceive the other; or does not perceive one, and does not know
and does not perceive the other; or has no perception or knowledge
of either--all these cases must be excluded. But he may err when he
confuses what he knows or perceives, or 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.
Theaetetus is delighted with this explanation. But Socrates has no
sooner found the new solution than he sinks into a fit of despondency.
For an objection occurs to him:--May there not be errors where there is
no confusion of mind and sense? e.g. in numbers. No one can confuse
the man whom he has in his thoughts with the horse which he has in his
thoughts, but he may err in the addition of five and seven. And observe
that these are purely mental conceptions. Thus we are involved once more
in the dilemma of saying, either that there is no such thing as false
opinion, or that a man knows what he does not know.
We are at our wit's end, and may therefore be excused for making a
bold diversion. All this time we have been repeating the words 'know,'
'understand,' yet we do not know what knowledge is. 'Why, Socrates,
how can you argue at all without using them?' Nay, but the true hero
of dialectic would have forbidden me to use them until I had explained
them. And I must explain them now. The verb 'to know' has two senses,
to have and to possess knowledge, and I distinguish 'having' from
'possessing.' A man may possess a garment which he does not wear; or he
may have wild birds in an aviary; these in one sense he possesses, and
in another he has none of them. Let this aviary be an image of the mind,
as the waxen block was; when we are young, the aviary is empty; after
a time the birds are put in; for under this figure we may describe
different forms of knowledge;--there are some of them in groups, and
some single, which are flying about everywhere; and let us suppose
a hunt after the science of odd and even, or some other science. The
possession of the birds is clearly not the same as the having them in
the hand. And the original chase of them is not the same as taking them
in the hand when they are already caged.
This distinction between use and possession saves us from the absurdity
of supposing that we do not know what we know, because we may know in
one sense, i.e. possess, what we do not know in another, i.e. use. But
have we not escaped one difficulty only to encounter a greater? For how
can the exchange of two kinds of knowledge ever become false opinion?
As well might we suppose that ignorance could make a man know, or that
blindness could make him see. Theaetetus suggests that in the aviary
there may be flying about mock birds, or forms of ignorance, and we
put forth our hands and grasp ignorance, when we are intending to grasp
knowledge. But how can he who knows the forms of knowledge and the forms
of ignorance imagine one to be the other? Is there some other form of
knowledge which distinguishes them? and another, and another? Thus we go
round and round in a circle and make no progress.
All this confusion arises out of our attempt to explain false opinion
without having explained knowledge. What then is knowledge? Theaetetus
repeats that knowledge is true opinion. But this seems to be refuted by
the instance of orators and judges. For surely the orator cannot convey
a true knowledge of crimes at which the judges were not present; he
can only persuade them, and the judge may form a true opinion and truly
judge. But if true opinion were knowledge they could not have judged
without knowledge.
Once more. Theaetetus offers a definition which he has heard: Knowledge
is true opinion accompanied by definition or explanation. Socrates has
had a similar dream, and has further heard that the first elements are
names only, and that definition or explanation begins when they are
combined; the letters are unknown, the syllables or combinations
are known. But this new hypothesis when tested by the letters of the
alphabet is found to break down. The first syllable of Socrates' name
is SO. But what is SO? Two letters, S and O, a sibilant and a vowel,
of which no further explanation can be given. And how can any one
be ignorant of either of them, and yet know both of them? There is,
however, another alternative:--We may suppose that the syllable has a
separate form or idea distinct from the letters or parts. The all of the
parts may not be the whole. Theaetetus is very much inclined to adopt
this suggestion, but when interrogated by Socrates he is unable to
draw any distinction between the whole and all the parts. And if the
syllables have no parts, then they are those original elements of which
there is no explanation. But how can the syllable be known if the letter
remains unknown? In learning to read as children, we are first taught
the letters and then the syllables. And in music, the notes, which
are the letters, have a much more distinct meaning to us than the
combination of them.
Once more, then, we must ask the meaning of the statement, that
'Knowledge is right opinion, accompanied by explanation or definition.'
Explanation may mean, (1) the reflection or expression of a man's
thoughts--but every man who is not deaf and dumb is able to express his
thoughts--or (2) the enumeration of the elements of which anything is
composed. A man may have a true opinion about a waggon, but then, and
then only, has he knowledge of a waggon when he is able to enumerate
the hundred planks of Hesiod. Or he may know the syllables of the name
Theaetetus, but not the letters; yet not until he knows both can he be
said to have knowledge as well as opinion. But on the other hand he may
know the syllable 'The' in the name Theaetetus, yet he may be mistaken
about the same syllable in the name Theodorus, and in learning to read
we often make such mistakes. And even if he could write out all the
letters and syllables of your name in order, still he would only have
right opinion. Yet there may be a third meaning of the definition,
besides the image or expression of the mind, and the enumeration of the
elements, viz. (3) perception of difference.
For example, I may see a man who has eyes, nose, and mouth;--that will
not distinguish him from any other man. Or he may have a snub-nose and
prominent eyes;--that will not distinguish him from myself and you and
others who are like me. But when I see a certain kind of snub-nosedness,
then I recognize Theaetetus. And having this sign of difference, I have
knowledge. But have I knowledge or opinion of this difference; if I
have only opinion I have not knowledge; if I have knowledge we assume
a disputed term; for knowledge will have to be defined as right opinion
with knowledge of difference.
And so, Theaetetus, knowledge is neither perception nor true opinion,
nor yet definition accompanying true opinion. And I have shown that the
children of your brain are not worth rearing. Are you still in labour,
or have you brought all you have to say about knowledge to the birth? If
you have any more thoughts, you will be the better for having got rid of
these; or if you have none, you will be the better for not fancying that
you know what you do not know. Observe the limits of my art, which, like
my mother's, is an art of midwifery; I do not pretend to compare with
the good and wise of this and other ages.
And now I go to meet Meletus at the porch of the King Archon; but
to-morrow I shall hope to see you again, Theodorus, at this place.
...
I. The saying of Theaetetus, that 'Knowledge is sensible perception,'
may be assumed to be a current philosophical opinion of the age. 'The
ancients,' as Aristotle (De Anim.) says, citing a verse of Empedocles,
'affirmed knowledge to be the same as perception.' We may now examine
these words, first, with reference to their place in the history of
philosophy, and secondly, in relation to modern speculations.
(a) In the age of Socrates the mind was passing from the object to the
subject. The same impulse which a century before had led men to form
conceptions of the world, now led them to frame general notions of the
human faculties and feelings, such as memory, opinion, and the like. The
simplest of these is sensation, or sensible perception, by which Plato