, both in the Cratylus
and Sophist. 'Theaetetus is flying,' is a sentence in form quite as
grammatical as 'Theaetetus is sitting'; the difference between the two
sentences is, that the one is true and the other false. But,
before making this appeal to common sense, Plato propounds for our
consideration a theory of the nature of the negative.

The theory is, that Not-being is relation. Not-being is the other of
Being, and has as many kinds as there are differences in Being.
This doctrine is the simple converse of the famous proposition of
Spinoza,--not 'Omnis determinatio est negatio,' but 'Omnis negatio est
determinatio';--not, All distinction is negation, but, All negation is
distinction. Not-being is the unfolding or determining of Being, and is
a necessary element in all other things that are. We should be careful
to observe, first, that Plato does not identify Being with Not-being; he
has no idea of progression by antagonism, or of the Hegelian vibration
of moments: he would not have said with Heracleitus, 'All things are
and are not, and become and become not.' Secondly, he has lost sight
altogether of the other sense of Not-being, as the negative of Being;
although he again and again recognizes the validity of the law of
contradiction. Thirdly, he seems to confuse falsehood with negation. Nor
is he quite consistent in regarding Not-being as one class of Being, and
yet as coextensive with Being in general. Before analyzing further the
topics thus suggested, we will endeavour to trace the manner in which
Plato arrived at his conception of Not-being.

In all the later dialogues of Plato, the idea of mind or intelligence
becomes more and more prominent. That idea which Anaxagoras employed
inconsistently in the construction of the world, Plato, in the Philebus,
the Sophist, and the Laws, extends to all things, attributing to
Providence a care, infinitesimal as well as infinite, of all creation.
The divine mind is the leading religious thought of the later works of
Plato. The human mind is a sort of reflection of this, having ideas
of Being, Sameness, and the like. At times they seem to be parted by a
great gulf (Parmenides); at other times they have a common nature, and
the light of a common intelligence.

But this ever-growing idea of mind is really irreconcilable with the
abstract Pantheism of the Eleatics. To the passionate language of
Parmenides, Plato replies in a strain equally passionate:--What! has
not Being