Knowledge, opposed to divine inspiration without knowledge.
Ion is willing enough (as he promises) to exhibit before Sokrates one of his eloquent discourses upon Homer. But Sokrates never permits him to arrive at it: arresting him always by preliminary questions, and requiring him to furnish an intelligible description of the matter which his discourse is intended to embrace, and thus to distinguish it from other matters left untouched. A man who cannot comply with this requisition, — who cannot (to repeat what I said in a previous chapter) stand a Sokratic cross-examination on the subject — possesses no rational intelligence of his own proceedings: no art, science, knowledge, system, or method. If as a practitioner he executes well what he promises (which is often the case), and attains success — he does so either by blind imitation of some master, or else under the stimulus and guidance of some agency foreign to himself — of the Gods or Fortune.
This is the Platonic point of view; developed in several different ways and different dialogues, but hardly anywhere more conspicuously than in the Ion.
Illustration of Plato’s opinion respecting the uselessness of written geometrical treatises.
I have observed that in this dialogue, Ion is anxious to embark on his eloquent expository discourse, but Sokrates will not allow him to begin: requiring as a preliminary stage that certain preliminary difficulties shall first be cleared up. Here we have an illustration of Plato’s doctrine, to which I adverted in a former chapter,[35] — that no written geometrical treatise could impart a knowledge of geometry to one ignorant thereof. The geometrical writer begins by laying down a string of definitions and axioms; and then strikes out boldly in demonstrating his theorems. But Plato would refuse him the liberty of striking out, until he should have cleared up the preliminary difficulties about the definitions and axioms themselves. This the geometrical treatise does not even attempt.[36]
[36] Compare Plato, Republic, vi. 510 C; vii. 538 C-D.