Imagine that the keeper of a huge, strong beast notices what makes it angry, what it desires, how it has to be approached and handled, the circumstances and the conditions under which it becomes particularly fierce or calm, what provokes its typical cries, and what tones of voice make it gentle or wild. Once he's spent enough time in the creature's company to acquire all this information, he calls it knowledge, forms it into a systematic branch of expertise, and starts to teach it, despite total ignorance, in fact, about which of the creature's attitudes and desires is commendable or deplorable, good or bad, moral or immoral. His usage of all these terms simply conforms to the great beast's attitudes, and he describes things as good or bad according to its likes and dislikes, and can't justify his usage of the terms any further, but describes as right and good the things which are merely indispensable, since he hasn't realised and can't explain to anyone else how vast a gulf there is between necessity and goodness.
Plato, The Republic
goodness