Recall: Philosophers, lovers wisdom, who want knowledge, a connection with what really is what it is, not what is only partly or imperfectly what is.
Now that we've got a definition, why let them rule?
Mending the world:
those who are verily and indeed wanting in the knowledge of the true being of each thing... [who] are unable as with a painters eye to look at the absolute truth and to that original to repair... and order the laws about beauty, goodness, justice... are not such persons, I ask, simply blind?
A noble nature most easily corrupted: Alcibiades
Evil and Greatnesss: "this being the class out of which comes the men who are the authors of the greatest evil to the state... and also the greatest good"
The captain of the mutiny?
Or the pilot?
imagine a man who should study the tempers of a mighty strong beast, which is fed by him... When, by continually attending upon [it] he has become perfect in [predicting its cries and groans] he calls this honourable and that dishonourable, or good and evil... all in accordance with the tastes and tempers of that great beast.
Why does the knowledge of the guardians qualify them for rule, and make them analogous to the pilot? They're not technical experts, like the cobbler or the shipbuilder.
What, in more detail, is the sort of thing that the guardians will know?
That without which, any other knowledge or possession of any kind will profit us nothing.
What is the good?
The many, as we say, are seen but not known, and the ideas are known but not seen
Not literal sight---that's the analogy
Without the addition of some other nature, there is no seeing or being seen
The sun (the child of the good) is to the faculty of sight, as the good is to the faculty of knowledge
when resting upon that on which truth and being shine, the soul perceives and understands, and is radiant with intelligence; but when turned towards the twilight of becoming and perishing, then she has opinion only, and goes blinking about, and is first of one opinion and then of another
Reflections - The Reflected - The Hypothetical - First Principles
there are their hypotheses, which they and everyone else are supposed to know, and they do not deign to give any account of them either to themselves or others... but they begin with them, and go on until they arrive, at last, and in a consistent manner, at their conclusion
using hypotheses not as first principles, but only as hypotheses---that is to say, steps and points of departure into a world above hypotheses... the first principles of the whole.