n already noticed, we cannot be much surprised that Plato should
have made classes of Not-being. It is observable that he does not
absolutely deny that there is an opposite of Being. He is inclined to
leave the question, merely remarking that the opposition, if admissible
at all, is not expressed by the term 'Not-being.'

On the whole, we must allow that the great service rendered by Plato
to metaphysics in the Sophist, is not his explanation of 'Not-being' as
difference. With this he certainly laid the ghost of 'Not-being'; and we
may attribute to him in a measure the credit of anticipating Spinoza
and Hegel. But his conception is not clear or consistent; he does not
recognize the different senses of the negative, and he confuses
the different classes of Not-being with the abstract notion. As the
Pre-Socratic philosopher failed to distinguish between the universal and
the true, while he placed the particulars of sense under the false and
apparent, so Plato appears to identify negation with falsehood, or is
unable to distinguish them. The greatest service rendered by him to
mental science is the recognition of the communion of classes, which,
although based by him on his account of 'Not-being,' is independent
of it. He clearly saw that the isolation of ideas or classes is the
annihilation of reasoning. Thus, after wandering in many diverging
paths, we return to common sense. And for this reason we may be inclined
to do less than justice to Plato,--because the truth which he attains
by a real effort of thought is to us a familiar and unconscious truism,
which no one would any longer think either of doubting or examining.

IV. The later dialogues of Plato contain many references to contemporary
philosophy. Both in the Theaetetus and in the Sophist he recognizes
that he is in the midst of a fray; a huge irregular battle everywhere
surrounds him (Theaet.). First, there are the two great philosophies
going back into cosmogony and poetry: the philosophy of Heracleitus,
supposed to have a poetical origin in Homer, and that of the Eleatics,
which in a similar spirit he conceives to be even older than Xenophanes
(compare Protag.). Still older were theories of two and three
principles, hot and cold, moist and dry, which were ever marrying and
being given in marriage: in speaking of these, he is probably referring
to Pherecydes and the early Ionians. In the philosophy of motion there
were different accounts of the relation of plur