[21] Plato, Kratyl. pp. 397, 425, 438.
Counter-Theory, which Sokrates here sets forth and impugns — the Protagorean doctrine — Homo Mensura.
In laying down the basis of his theory respecting names, Plato states another doctrine as opposed to it: viz., the Protagorean doctrine — Man is the Measure of all things. I have already said something about this doctrine, in reviewing the Theætêtus, where Plato impugns it: but as he here impugns it again, by arguments in part different — a few words more will not be misplaced.
The doctrine of Protagoras maintains that all things are relative to the percipient, cogitant, concipient, mind: that all Object is implicated with a Subject: that as things appear to me, so they are to me — as they appear to you, so they are to you. Plato denies this, and says: “All things have a fixed essence of their own, absolutely and in themselves, not relative to any percipient or cogitant — nor dependent upon any one’s appreciative understanding, or emotional susceptibility, or will. Things are so and so, without reference to us as sentient or cogitant beings: and not only the things are thus independent and absolute, but all their agencies are so likewise — agencies either by them or upon them. Cutting, burning, speaking, naming, &c., must be performed in a certain determinate way, whether we prefer it or not. A certain Name belongs, by Nature or absolutely, to a certain thing, whether we choose it or not: it is not relative to any adoption by us, either individually or collectively.”
This Protagorean theory is here set forth by the Platonic Sokrates as the antithesis or counter-theory, to that which he is himself advancing, viz. — That Names are significant by nature and not by agreement of men:— That each Nomen is tied to its Nominatum by a natural and indissoluble bond. His remarks imply, that those who do not accept this last-mentioned theory must agree with Protagoras. But such an antithesis is noway necessary: since (not to speak of Hermogenes himself in this very dialogue) we find also that Aristotle — who maintains that Names are significant by convention and not by nature — dissents also from the theory of Protagoras: and would have rested his dissent from it on very different grounds.
Objection by Sokrates — That Protagoras puts all men on a level as to wisdom and folly, knowledge and ignorance.
This will show us — what I have already remarked in commenting on the Theætêtus — that Plato has not been very careful in appreciating the real bearing of the Protagorean doctrine. He impugns it here by the same argument which we also read in the Theætêtus. “Everyone admits” (he says) “that there are some men wise and good — others foolish and wicked. Now if you admit this, you disallow the Protagorean doctrine. If I contend that as things appear to me, so they truly are to me — as things appear to you or to him, so they truly are to you or to him — I cannot consistently allow that any one man is wiser than any other. Upon such a theory, all men are put upon the same level of knowledge or ignorance.”
But the premisses of Plato here do not sustain his inference.
Objection unfounded — What the Protagorean theory really affirms — Belief always relative to the believer’s mind.
The Protagorean doctrine is, when stated in its most general terms, — That every man is and must be his own measure of truth or falsehood — That what appears to him true, is true to him, however it may appear to others — That he cannot by any effort step out of or beyond his own individual belief conviction, knowledge — That all his Cognita, Credita, Percepta, Cogitata, &c., imply himself as Cognoscens, Credens, Percipiens, Cogitans, inseparably and indivisibly — That in affirming an object, he himself is necessarily present as affirming subject, and that Object and Subject are only two sides of the same indivisible fact[22] — That though there are some matters which all men agree in believing, there is no criterion at once infallible and universally recognised, in matters where they dissent: moreover, the matters believed are just as much relative where all agree, as where some disagree.