The Timaeus of Plato

22 INTRODUCTION.
generate a percept without subject. And subject as well as object
is
undergoing perpetual mutation thus, since a change either of
:
object or of subject singly involves a change in the perception,
every perception is continually suffering a twofold alteration.
Perception is therefore an ever-flowing stream, incessantly changing
its character in correspondence with the changes in subject and
in object. Nothing therefore can be more complete than the
absolute instability of our sensuous perceptions. The importance
of this theory will be better realised when we view it in the light
of the Timaeus.
The 21. More important than even the Parmenides is the
Sop is . Sophist, one of the most profound and far-reaching of Plato's
works. Plato starts with an endeavour to define the sophist, who,
when accused of teaching what seems to be but is not knowledge,
turns upon us, protesting the impossibility of predicating notbeing
: it is nonsense to say he teaches what is not, for TO p? oi/
can neither be thought nor uttered. Hereupon follows a truly
masterly examination into the logic of being and not-being. The
result is to show that either of the two, viewed in the abstract
and apart from the other, is self-contradictory and unthinkable.
And as being cannot exist without not-being, so unity also, if
it is to have any intelligible existence, must contain in itself the
element of plurality ;
one is at the same time one and not-one,
else it has no meaning. The failure to grasp
this truth is the
fundamental flaw in Eleatic metaphysics and consequently in the
earlier ideal theory. It seems to me hardly open to doubt that
the eiSwv