The two personalities (my notion)
Jim is vital, independent, with a strong core and mild manners, one who can control his own life; yet his attitude towards the women is rather problematic, similar to that of Catherine respectively towards the men. Jules seems to be his antipode - passive, psychically dependant, one who accepts everything not because his heart of gold but for he values his own peace of mind more than anything else; obviously he has been spoiled by his wealthy family; and thus his manners are somewhat rigid (you may clearly see it following his image carefully).
Although Catherine is rather unsympathetic, one should recognize her huge vital strength that "nurtured" Jules and Jim. She wasn't a "goddess", but both men needed her vitality as a psychic source.
All that was captured by Truffault with exceptional wisdom and talent; he shows the greatest respect to his audiences by the way of giving them "the space" for judgement.
Listen to your enemy, for God is talking