Both Uses

intellectual
in
Allegory of the Cave
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This entire allegory, I said, you may now append, dear Glaucon, to the previous argument; the prison-house is the world of sight, the light of the fire is the sun, and you will not misapprehend me if you interpret the journey upwards to be the ascent of the soul into the intellectual world according to my poor belief, which, at your desire, I have expressed— whether rightly or wrongly God knows.†
*
But, whether true or false, my opinion is that in the world of knowledge the idea of good appears last of all, and is seen only with an effort; and, when seen, is also inferred to be the universal author of all things beautiful and right, parent of light and of the lord of light in this visible world, and the immediate source of reason and truth in the intellectual; and that this is the power upon which he who would act rationally either in public or private life must have his eye fixed.†

Definitions:

(1) (intellectual as in: intellectual stimulation)
related to intelligence -- such as requiring, appealing to, or possessing intelligence
(2) (intellectual as in: She is an intellectual.)
a highly educated person interested in learning and exploring ideas -- sometimes while ignoring practical considerations
(3) (meaning too rare to warrant focus)