Last in the order of exposition, in the Republic, of what the true lover of wisdom will want to learn, and of what the imagined philosopher-rulers will be brought to ‘see’, comes the ‘greatest’ subject of all, the ‘greatest object for learning’ (to megiston mathēma, vi, 504d2–3, etc.). Adimantus expresses surprise that there could be any greater subject to be learned about than the ones they've already treated, i.e. justice and the other excellences – to which Socrates retorts that Adimantus already pretty well knows what this new subject is, because he's heard about it often enough (a point that will be repeatedly reinforced): it's the form of the good (hē tou agathou idea, 505a2), which is what makes just things and the rest useful and beneficial (sc. so that it really is a more important subject than justice and the other excellences). Adimantus also knows that ‘we’ (humanity in general?) don't have adequate knowledge of the good – and if we don't have knowledge of it, then even the most complete knowledge of the rest will be of no use to us, any more than if we merely possess something without its also being good for us.