Theaetetus
'The excellent Socrates has first confused me with Heracleitus, and
Heracleitus with his Ephesian successors, and has then disproved the
existence both of knowledge and sensation. But I am not responsible
for what I never said, nor will I admit that my common-sense account of
knowledge can be overthrown by unintelligible Heraclitean paradoxes.'
IV. Still at the bottom of the arguments there remains a truth, that
knowledge is something more than sensible perception;--this alone would
not distinguish man from a tadpole. The absoluteness of sensations
at each moment destroys the very consciousness of sensations (compare
Phileb.), or the power of comparing them. The senses are not mere holes
in a 'Trojan horse,' but the organs of a presiding nature, in which they
meet. A great advance has been made in psychology when the senses
are recognized as organs of sense, and we are admitted to see or feel
'through them' and not 'by them,' a distinction of words which, as
Socrates observes, is by no means pedantic. A still further step has
been made when the most abstract notions, such as Being and Not-being,
sameness and difference, unity and plurality, are acknowledged to be the
creations of the mind herself, working upon the feelings or impressions
of sense. In this manner Plato describes the process of acquiring them,
in the words 'Knowledge consists not in the feelings or affections
(pathemasi), but in the process of reasoning about them (sullogismo).'
Here, is in the Parmenides, he means something not really different
from generalization. As in the Sophist, he is laying the foundation of a
rational psychology, which is to supersede the Platonic reminiscence of
Ideas as well as the Eleatic Being and the individualism of Megarians
and Cynics.
V. Having rejected the doctrine that 'Knowledge is perception,' we now
proceed to look for a definition of knowledge in the sphere of opinion.
But here we are met by a singular difficulty: How is false opinion
possible? For we must either know or not know that which is presented
to the mind or to sense. We of course should answer at once: 'No; the
alternative is not necessary, for there may be degrees of knowledge; and
we may know and have forgotten, or we may be learning, or we may have a
general but not a particular knowledge, or we may know but not be able
to explain;' and many other ways may be imagined in which we know and do
not know at the same time. But these answers belong to a later stage of
metaphysical discussion; whereas the difficulty in question naturally
arises owing to the childhood of the human mind, like the parallel
difficulty respecting Not-being. Men had only recently arrived at the
notion of opinion; they could not at once define the true and pass
beyond into the false. The very word doxa was full of ambiguity, being
sometimes, as in the Eleatic philosophy, applied to the sensible world,
and again used in the more ordinary sense of opinion. There is no
connexion between sensible appearance and probability, and yet both
of them met in the word doxa, and could hardly be disengaged from one
another in the mind of the Greek living in the fifth or fourth century
B.C. To this was often added, as at the end of the fifth book of the
Republic, the idea of relation, which is equally distinct from either of
them; also a fourth notion, the conclusion of the dialectical process,
the making up of the mind after she has been 'talking to herself'
(Theat.).
We are not then surprised that the sphere of opinion and of Not-being
should be a dusky, half-lighted place (Republic), belonging neither
to the old world of sense and imagination, nor to the new world of
reflection and reason. Plato attempts to clear up this darkness. In
his accustomed manner he passes from the lower to the higher, without
omitting the intermediate stages. This appears to be the reason why he
seeks for the definition of knowledge first in the sphere of opinion.
Hereafter we shall find that something more than opinion is required.
False opinion is explained by Plato at first as a confusion of mind and
sense, which arises when the impression on the mind does not correspond
to the impression made on the senses. It is obvious that this
explanation (supposing the distinction between impressions on the mind
and impressions on the senses to be admitted) does not account for all
forms of error; and Plato has excluded himself from the consideration of
the greater number, by designedly omitting the intermediate processes
of learning and forgetting; nor does he include fallacies in the use of
language or erroneous inferences. But he is struck by one possibility
of error, which is not covered by his theory, viz. errors in arithmetic.
For in numbers and calculation there is no combination of thought and
sense, and yet errors may often happen. Hence he is led to discard the
explanation which might nevertheless have been supposed to hold good
(for anything which he says to the contrary) as a rationale of error, in
the case of facts derived from sense.
Another attempt is made to explain false opinion by assigning to error
a sort of positive existence. But error or ignorance is essentially
negative--a not-knowing; if we knew an error, we should be no longer in
error. We may veil our difficulty under figures of speech, but these,
although telling arguments with the multitude, can never be the real
foundation of a system of psychology. Only they lead us to dwell upon
mental phenomena which if expressed in an abstract form would not be
realized by us at all. The figure of the mind receiving impressions is
one of those images which have rooted themselves for ever in language.
It may or may not be a 'gracious aid' to thought; but it cannot be
got rid of. The other figure of the enclosure is also remarkable as
affording the first hint of universal all-pervading ideas,--a notion
further carried out in the Sophist. This is implied in the birds, some
in flocks, some solitary, which fly about anywhere and everywhere. Plato
discards both figures, as not really solving the question which to us
appears so simple: 'How do we make mistakes?' The failure of the enquiry
seems to show that we should return to knowledge, and begin with that;
and we may afterwards proceed, with a better hope of success, to the
examination of opinion.
But is true opinion really distinct from knowledge? The difference
between these he seeks to establish by an argument, which to us appears
singular and unsatisfactory. The existence of true opinion is proved
by the rhetoric of the law courts, which cannot give knowledge, but
may give true opinion. The rhetorician cannot put the judge or juror in
possession of all the facts which prove an act of violence, but he may
truly persuade them of the commission of such an act. Here the idea of
true opinion seems to be a right conclusion from imperfect knowledge.
But the correctness of such an opinion will be purely accidental; and is
really the effect of one man, who has the means of knowing, persuading
another who has not. Plato would have done better if he had said that
true opinion was a contradiction in terms.
Assuming the distinction between knowledge and opinion, Theaetetus, in
answer to Socrates, proceeds to define knowledge as true opinion, with
definite or rational explanation. This Socrates identifies with another
and different theory, of those who assert that knowledge first begins
with a proposition.
The elements may be perceived by sense, but they are names, and cannot
be defined. When we assign to them some predicate, they first begin to
have a meaning (onomaton sumploke logou ousia). This seems equivalent
to saying, that the individuals of sense become the subject of knowledge
when they are regarded as they are in nature in relation to other
individuals.
Yet we feel a difficulty in following this new hypothesis. For must not
opinion be equally expressed in a proposition? The difference between
true and false opinion is not the difference between the particular and
the universal, but between the true universal and the false. Thought may
be as much at fault as sight. When we place individuals under a
class, or assign to them attributes, this is not knowledge, but a very
rudimentary process of thought; the first generalization of all, without
which language would be impossible. And has Plato kept altogether clear
of a confusion, which the analogous word logos tends to create, of a
proposition and a definition? And is not the confusion increased by the
use of the analogous term 'elements,' or 'letters'? For there is no real
resemblance between the relation of letters to a syllable, and of the
terms to a proposition.
Plato, in the spirit of the Megarian philosophy, soon discovers a flaw
in the explanation. For how can we know a compound of which the simple
elements are unknown to us? Can two unknowns make a known? Can a whole
be something different from the parts? The answer of experience is that
they can; for we may know a compound, which we are unable to analyze
into its elements; and all the parts, when united, may be more than all
the parts separated: e.g. the number four, or any other number, is more
than the units which are contained in it; any chemical compound is more
than and different from the simple elements. But ancient philosophy
in this, as in many other instances, proceeding by the path of mental
analysis, was perplexed by doubts which warred against the plainest
facts.
Three attempts to explain the new definition of knowledge still remain
to be considered. They all of them turn on the explanation of logos. The
first account of the meaning of the word is the reflection of thought in
speech--a sort of nominalism 'La science est une langue bien faite.' But
anybody who is not dumb can say what he thinks; therefore mere speech
cannot be knowledge. And yet we may observe, that there is in this
explanation an element of truth which is not recognized by Plato; viz.
that truth and thought are inseparable from language, although mere
expression in words is not truth. The second explanation of logos is the
enumeration of the elementary parts of the complex whole. But this is
only definition accompanied with right opinion, and does not yet attain
to the certainty of knowledge. Plato does not mention the greater
objection, which is, that the enumeration of particulars is endless;
such a definition would be based on no principle, and would not help us
at all in gaining a common idea. The third is the best explanation,--the
possession of a characteristic mark, which seems to answer to the
logical definition by genus and difference. But this, again, is equally
necessary for right opinion; and we have already determined, although
not on very satisfactory grounds, that knowledge must be distinguished
from opinion. A better distinction is drawn between them in the Timaeus.
They might be opposed as philosophy and rhetoric, and as conversant
respectively with necessary and contingent matter. But no true idea of
the nature of either of them, or of their relation to one another, could
be framed until science obtained a content. The ancient philosophers
in the age of Plato thought of science only as pure abstraction, and to
this opinion stood in no relation.
Like Theaetetus, we have attained to no definite result. But an
interesting phase of ancient philosophy has passed before us. And the
negative result is not to be despised. For on certain subjects, and in
certain states of knowledge, the work of negation or clearing the ground
must go on, perhaps for a generation, before the new structure can begin
to rise. Plato saw the necessity of combating the illogical logic of
the Megarians and Eristics. For the completion of the edifice, he makes