There is here no question of repugnancy or intercommunion of Forms: the question turns upon the evidence of vision, which informs us that Theætêtus is sitting down and not standing up or flying. If any predicate be affirmed of a subject, contrary to what is included in the definition of that subject, then indeed repugnancy of Forms might be urged.
[153] Plato, Sophist. p. 257 B.
What must be assumed in all dialectic discussion.
In all reasoning, nay in all communication by speech, you must assume that your hearer understands the meaning of what is spoken: that he has the feelings of belief and disbelief, and is familiar with those forms of the language whereby such feelings are expressed: that there are certain propositions which he believes — in other words, which he regards as true: that there are certain other propositions which he disbelieves, or regards as false: that he has had experience of the transition from belief to disbelief, and vice versâ — in other words, of having fallen into error and afterwards come to perceive that it was error. These are the mental facts realised in each man and assumed by him to be also realised in his neighbours, when communication takes place by speech. If a man could be supposed to believe nothing, and to disbelieve nothing; — if he had no forms of speech to express his belief, disbelief, affirmation, and denial — no information could be given, no discussion would be possible. Every child has to learn this lesson in infancy; and a tedious lesson it undoubtedly is.[154] Antisthenes (who composed several dialogues) and the other disputants of whom we are now speaking, must have learnt the lesson as other men have: but they find or make some general theory which forbids them to trust the lesson when learnt. It was in obedience to some such theory that Antisthenes discarded all predication except essential predication, and discarded also the form suited for expressing disbelief — the negative proposition: maintaining, That to contradict was impossible. I know no mode of refuting him, except by showing that his fundamental theory is erroneous.
[154] Aristotel. Metaphys. vii. 1043, b. 25. ὥστε ἡ ἀπορία ἣν οἱ Ἀντισθένειοι καὶ οἱ οὕτως ἀπαίδευτοι ἠπόρουν, ἔχει τινὰ καιρόν, &c.
Compare respecting this paradox or θέσις of Antisthenes, the scholia of Alexander on the passage of Aristotle’s Topica above cited, p. 259, b. 15, in Schol. Bekk.
If Antisthenes admitted only identical predications, of course τὸ ἀντιλόγειν became impossible. I have endeavoured to show, in a previous [note] on this dialogue, that a misconception (occasionally shared even by Plato) of the function of the copula, lay at the bottom of the Antisthenean theory respecting identical predication. Compare Aristotel. Physic. i. p. 185, b. 28, together with the Scholia of Simplikius, pp. 329-330, ed. Bekk., and Plato, Sophistês, p. 245.
Discussion and theorising presuppose belief and disbelief, expressed in set forms of words. They imply predication, which Antisthenes discarded.
Discussion and theorising can only begin when these processes, partly intellectual, partly emotional, have become established and reproducible portions of the train of mental association. As processes, they are common to all men. But though two persons agree in having expressed the feeling of belief, and in expressing that feeling by one form of proposition — also in having the feeling of disbelief, and in expressing it by another form of proposition — yet it does not follow that the propositions which these two believe or disbelieve are the same. How far such is the case must be ascertained by comparison — by appeal to sense, memory, inference from analogy, induction, feeling, consciousness, &c. The ground is now prepared for fruitful debate: for analysing the meaning, often confused and complicated, of propositions: for discriminating the causes, intellectual and emotional, of belief and disbelief, and for determining how far they harmonise in one mind and another: for setting out general rules as to sequence, or inconsistency, or independence, of one belief as compared with another. To a certain extent, the grounds of belief and disbelief in all men, and the grounds of consistency or inconsistency between some beliefs and others, will be found to harmonise: they can be embodied in methodical forms of language, and general rules can be laid down preventing in many cases inadvertence or erroneous combination. It is at this point that Aristotle takes up rational grammar and logic, with most profitable effect. But he is obliged to postulate (what Antisthenes professed to discard) predication, not merely identical, but also accidental as well as essential — together with names and propositions both negative and affirmative.[155] He cannot avoid postulating thus much: though he likewise postulates a great deal more, which ought not to be granted.
[155] See the remarks in Aristotel. Metaphys. Γ. 1005, b. 2, 1006, a. 6. He calls it ἀπαιδευσία — ἀπαιδευσία τῶν ἀναλυτικῶν — not to be able to distinguish those matters which can be proved and require to be proved, from those matters which are true, but require no proof and are incapable of being proved. But this distinction has been one of the grand subjects of controversy from his day down to the present day; and between different schools of philosophers, none of whom would allow themselves to deserve the epithet of ἀπαίδευτοι.