 … but Speusippus said that, since of things some are perceptible and others intelligible, the criterion of the intelligible ones is the scientific account, and that of the perceptible ones is the scientific perception. Scientific perception he understood to be that which partakes of the truth in accordance with the account. For just as the fingers of the flautist or harpist have an artistic actuality, yet one that is not completed in them in the first instance, but perfected on the basis of discipline conforming to reasoning, and as the perception of the musician has an actuality that can grasp what is in tune and what is out of tune, and this is not self-grown but comes about on the basis of reasoning, so also the scientific perception partakes of its scientific practice as naturally derived from the account, leading to the unerring discrimination of the subjects.