2 Glaucon's and Adeimantus' request to Socrates in Book II of the Republic is at times interpreted as if the brothers were asking Socrates to show that justice was an ultimate value, an end in itself, rather than just an instrumental good that was good for, beneficial to, its possessor. But this is a misinterpretation. The distinction they make between intrinsic and extrinsic goodness, goodness “by nature” and goodness “by opinion” (367C), is not one between absolute goodness in itself and relative, instrumental goodness. Glaucon and Adeimantus explicitly say that what they want to know about justice and injustice is “what effect (dynamis) each has in itself on the soul that has it, regardless of (later, social) rewards and consequences” (358B), “what power (dynamis) each has by itself on the possessor in whose soul it dwells, (even if it is) hidden from gods and men” (366E), “what each of itself does to its possessor” even if one takes away the social reputation attached to each (367B, E). They are not asking Socrates to show that justice is good in itself, regardless of any benefits it may bring to, any good effect it may have on, its possessor. This is clear from the examples of intrinsic goods (harmless pleasures and joys) and intrinsic and extrinsic goods (knowledge, sight, health) they give. Pleasure and joy are not good in themselves but only good for, in the life of, a being capable of experiencing them and naturally rejoicing in them. Knowledge is an intrinsic good not in itself but only for a rational being who finds the acquisition of knowledge, the exercise of his rational faculties, inherently satisfactory (even apart from the long-run, extrinsic benefits knowledge brings to its possessor). Health is neither good nor meaningful “in itself”: it can be meaningful and good only in reference to some living organism whose well-functioning can be in question. For such an organism health is intrinsically pleasurable as well as beneficial in the long run.
