This makes most sense if we take Abelard to be thinking that intentions have to tick two boxes in order to be good. Firstly, the person involved must believe that what they are intending is right; secondly, the intention must in fact actually be right, that is, actually be what God would want (§109). Thus, his advice for those who would avoid sin is to do whatever you sincerely believe is right. In order to do genuine good, though, your belief will need to be correct.
