The Rhetorical teachers conceived the Art too narrowly: Plato conceived it too widely. The principles of an Art are not required to be explained to all learners.
The teaching of these rhetors thus contributed to the security, dignity, and usefulness of the citizens, by arming them for public speech and action. But it was essentially practical, or empirical: it had little system, and was founded upon a narrow theory. Upon these points Plato in the Phædrus attacks them. He sets little value upon the accomplishments arming men for speech and action (λεκτικοὺς καὶ πρακτικοὺς εἶναι) — and he will not allow such teaching to be called an Art. He explains, in opposition to them, what he himself conceived the Art of Rhetoric to be, in the comprehensive way which I have above described.
But if the conception of the Art, as entertained by the Rhetors, is too narrow — that of Plato, on the other hand, is too wide.
First, it includes the whole basis of science or theory on which the Art rests: it is a Philosophy of Rhetoric, expounded by a theorist — rather than an Art of Rhetoric, taught to learners by a master. To teach the observance of certain rules or precepts is one thing: to set forth the reasons upon which those rules are founded, is another — highly important indeed, and proper to be known by the teacher; yet not necessarily communicated, or even communicable, to all learners. Quintilian, in his Institutio Rhetorica, gives both:— an ample theory, as well as an ample development of rules, of his professional teaching. But he would not have thought himself obliged to give this ample theory to all learners. With many, he would have been satisfied to make them understand the rules, and to exercise them in the ready observance thereof.
Plato includes in his conception of Art, the application thereof to new particular cases. — This can never be taught by rule.
Secondly, Plato, in defining the Art of Rhetoric, includes not only its foundation of science (which, though intimately connected with it, ought not to be considered as a constituent part), but also the application of it to particular cases; which application lies beyond the province both of science and of art, and cannot be reduced to any rule. “The Rhetor” (says Plato) “must teach his pupils, not merely to observe the rules whereby persuasion is operated, but also to know the particular persons to whom those rules are to be applied — on what occasions — within what limits — at what peculiar moments, &c.[114] Unless the Rhetor can teach thus much, his pretended art is no art at all: all his other teaching is of no value.” Now this is an amount of exigence which can never be realised. Neither art nor science can communicate that which Plato here requires. The rules of art, together with many different hypothetical applications thereof, may be learnt: when the scientific explanation of the rules is superadded, the learner will be assisted farther towards fresh applications: but after both these have been learnt, the new cases which will arise can never be specially foreseen. The proper way of applying the general precepts to each case must be suggested by conjecture adapted to the circumstances, under the corrections of past experience.[115] It is inconsistent in Plato, after affirming that nothing deserves the name of art[116] except what is general — capable of being rationally anticipated and prescribed beforehand — then to include in art the special treatment required for the multiplicity of particular cases; the analogy of the medical art, which he here instructively invokes, would be against him on this point.
[114] Plato, Phædr. pp. 268 B, 272 A.
[115] What Longinus says about critical skill is applicable here also — πολλῆς ἔστι πείρας τελευταῖον ἐπιγέννημα. Isokrates (De Permut. Or. xv. sect. 290-312-316) has some good remarks about the impossibility of ἐπιστήμη respecting particulars. Plato, in the Gorgias, puts τέχνη, which he states to depend upon reason and foreknowledge, in opposition to ἐμπειρία and τριβή, which he considers as dependant on the φύσις στοχαστική. But in applying the knowledge or skill called Art to particular cases, the φύσις στοχαστικὴ is the best that can be had (p. 463 A-B). The conception of τέχνη given in the Gorgias is open to the same remark as that which we find in the Phædrus. Plato, in another passage of the Phædrus, speaks of the necessity that φύσις, ἐπιστήμη, and μελέτη, shall concur to make an accomplished orator. This is very true; and Lysias, Isokrates, and all the other rhetors whom Plato satirises, would have concurred in it. In his description of τέχνη and ἐπιστήμη, and in the estimate which he gives of all that it comprises, he leaves no outlying ground for μελέτη. Compare Xenophon, Memor. iii. 1, 11; also Isokrates contra Sophistas, a. 16; and a good passage of Dionysius Halik. De Compos. Verborum, in which that rhetor remarks that καιρὸς or opportunity neither has been nor can be reduced to art and rule.
[116] Plato, Gorgias, pp. 464-465.
Plato’s charge against the Rhetorical teachers is not made out.