In Plato’s theory of Forms, the Form of the Good is at the top of the hierarchy of Forms, illuminating all of the others—knowledge of the good is required for knowledge of anything else.
In naturalistic terms, we can see this play out in the evolutionary imperatives of perception: An organism’s umwelt—the world as experienced by that organism—is comprised of those aspects of its environment in which it has been given an interest—can judge as good or bad, relative to its survival.