Discourses: Book 2 17 : 2
So it stands here also, in the affairs of life. Who among us has not upon his lips the words "good" and "evil," "advantageous" and "disadvantageous"? For who among us does not have a preconceived idea of each of these terms? Very well, is it fitted into a system and complete? Prove that it is. "How shall I prove it?" Apply it properly to specific facts. To start with, Plato classifies definitions under the preconception "the useful," but you classify them under that of "the useless." Is it, then, possible for both of you to be right? How can that be? Does not one man apply his preconceived idea of "the good" to the fact of wealth, while another does not? And another to that of pleasure, and yet another to that of health? Indeed, to sum up the whole matter, if all of us who have these terms upon our lips possess no mere empty knowledge of each one severally, and do not need to devote any pains to the systematic arrangement of our preconceived ideas, why do we disagree, why fight, why blame one another?