At the gates of the city of Megara in 369 BCE, Eucleides and Terpsion
hear a slave read out Eucleides' memoir of a philosophical discussion
that took place in 399 BCE, shortly before Socrates' trial and
execution (142a-143c). In this, the young Theaetetus is introduced to
Socrates by his mathematics tutor, Theodorus. Socrates questions
Theaetetus about the nature of expertise, and this leads him to pose
the key question of the dialogue: “What is knowledge?”
(143d-145e). Theaetetus' first response (D0) is to
give examples of knowledge such as geometry, astronomy, harmony,
arithmetic (146a-c). Socrates objects that, for any
x,
examples of
x are neither necessary nor sufficient for a
definition of
x (146d-147e). Theaetetus admits this, and
contrasts the ease with which he and his classmates define
mathematical terms with his inability to define of knowledge
(147c-148e). Socrates offers to explain Theaetetus' bewilderment about
the question “What is knowledge?” by comparing himself
with a midwife: Theaetetus, he suggests, is in discomfort because he
is in intellectual labour (148e-151d).
Thus prompted, Theaetetus states his first acceptable definition,
which is the proposal (D1) that “Knowledge is
perception” (151d-e). Socrates does not respond to this
directly. Instead he claims that D1 entails two other
theories (Protagoras' and Heracleitus'), which he expounds (151e-160e)
and then criticises (160e-183c). Socrates eventually presents no fewer
than eleven arguments, not all of which seem seriously intended,
against the Protagorean and Heracleitean views. If any of these
arguments hit its target, then by
modus tollens
D1 is also false. A more direct argument against
D1 is eventually given at 184-7.
In 187b4-8, Theaetetus proposes a second definition of knowledge:
(D2) “Knowledge is true belief.”
D2 provokes Socrates to ask: how can there be any
such thing as
false belief? There follows a five-phase
discussion which attempts to come up with an account of false
belief. All five of these attempts fail, and that appears to be the
end of the topic of false belief. Finally, at 200d-201c, Socrates
returns to D2 itself. He dismisses
D2 just by arguing that accidental true beliefs
cannot be called
knowledge, giving Athenian jurymen as an
example of accidental true belief.
Theaetetus tries a third time. His final proposal
(D3) defines knowledge as
“true belief
with an account (
logos)” (201c-d). The ensuing
discussion attempts to spell out what it might be like for
D3 to be true, then makes three attempts to spell out
what a
logos is.
In 201d-202d, the famous passage known as
The Dream of
Socrates, a two-part ontology of elements and complexes is
proposed. Parallel to this ontology runs a theory of explanation that
claims that to explain, to offer a
logos, is to analyse
complexes into their elements, i.e., those parts which cannot be
further analysed. Crucially, the Dream Theory says that knowledge of
O is true belief about
O plus an account of
O's composition. If
O is not composite,
O
cannot be known, but only “perceived” (202b6). When
Socrates argues against the Dream Theory (202d8-206b11), it is this
entailment that he focuses on.
Socrates then turns to consider, and reject, three attempts to spell
out what a
logos is—to give an account of
“account.” The first attempt takes
logos just to
mean “speech” or “statement” (206c-e). The
second account (206e4-208b12) of “
logos of
O” takes it as “enumeration of the elements of
O.” The third and last proposal (208c1-210a9) is that
to give the
logos of
O is to cite the
sêmeion or
diaphora of
O, the
“sign” or diagnostic feature wherein
O differs
from everything else.
All three attempts to give an account of “account”
fail. The day's discussion, and the dialogue, end in
aporia.
Socrates leaves to face his enemies in the courtroom.
(filler text lifted from http://plato.stanford.edu/entries/plato-theaetetus/#SumDia, trademark them, this post is going down as soon as we have real stuff on here.)
