1. For Socrates on unintentional misdeeds, see Hippias Minor. But the full Socratk doctrineas corroborated there plays no put in Hippias Major, all that is happening here is that the idea of ‘ability’ is being extended to its full range.

2. This turn of the argument shows that the substitution of ‘ability’ for ‘usefulness’ isimplausible: we would not say (and neither would a Greek) that error is the result of usefulness. The fact that, as Socrates has just argued, ability is a necessary prerequisite of usefulness doesnot justify the substitution. Plato’s mistake is not serious, however; it merely makes more long-winded the argument that ‘beneficial’ is the proper rawing of ‘useful’ in this context.