The young Theaetetus will have to undergo questioning by Socrates in order to see the noetic implications of his own mathematical discoveries, which advance beyond Pythagorean learning. Conversation with Theaetetus and Theodorus may very well show that the mathematician is more capable than the pragmatic politician in judging human souls. Socrates, the barren midwife of other people's insights, knows the difference between insight and mere opinion. He is expert at judging ideas which he can not himself produce. But the geometry of Theaetetus is not yet ready for Platonic dialectic.
Pythagorean mathematics is still too tied to sense-perception.
Mathematics itself must cross the divided line between opinion and knowledge before it can lead the way to dialectic. Mathematics must understand itself as knowledge of forms and not merely as construction of images. But there is a further difficulty. Socrates claims that a midwife, who can tell a good result from a bad one, is also a competent matchmaker. Socrates knows how to match up teachers and learners.