But if only a few grasp their entire duty in the matter of material charity, still fewer are those who understand and practice that of spiritual charity. And worse, people imagine that the spiritual care for one's neighbour is an affair of priests only, whereas, if indeed it is for these a duty of sheer justice, for the simple laity it becomes, precisely, a duty of charity. Hence people fancy they have done everything when they have taken thought for their own soul. If God turned today to each Christian and asked the same question He once asked of Cain, the majority would give Him the same answer: "Am I my brother's keeper?" (Gen. 4:9). This spiritual egoism, a widespread and most harmful disease, can be cured by prompt and energetic treatment. And the best is this: to teach and inculcate the duty of the apostolate, which is a holy altruism, a spiritual charity, "Contraries are cured by contraries".
( A Manual of Catholic Action, page 46)