Book 6: The Intellectual Virtues.
The faculty of intelligence or sound intelligence, in respect of which we say a man is intelligent or of sound intelligence, is not the same as science generally, nor as opinion (for then all men would be intelligent), nor is it identical with any particular science, such as medicine, which deals with matters of health, and geometry, which deals with magnitudes; for intelligence has not to do with what is eternal and unchangeable, nor has it to do with events of every kind, but only with those that one may doubt and deliberate about. And so it has to do with the same matters as prudence; but they are not identical: prudence issues orders, for its scope is that which is to be done or not to be done; while intelligence discerns merely (intelligence being equivalent to sound intelligence, and an intelligent man to a man of sound intelligence).
Intelligence, in fact, is equivalent neither to the possession nor to the acquisition of prudence; but just as the learner in science is said to show intelligence when he makes use of the scientific knowledge which he hears from his teacher, so in the domain of prudence a man is said to show intelligence when he makes use of the opinions which he hears from others in judging, and judging fitly—for soundly [when we speak of sound intelligence] means fitly.
And from this use of the term with regard to learning comes its employment to denote that faculty which we imply when we call a man intelligent; for we often speak of the intelligence of a learner.