The context of the line is a point when Stephen awakens to the spiritual dimension both within himself and in the world. The continual repetition of the infernal condemnation of hell and the transgressions that Stephen has committed in turning his back to the divine begin to haunt at Stephen. His own consciousness becomes filled with the feelings of regret. Stephen wishes to fall upon the mercy of the divine force that he has denied in the world, a force whose reality has been illuminated by the sermons he has absorbed.
In this context, the line presents itself. On one hand, it sounds as if Stephen is pleading for his own soul, calling out to a divine force to forgive. It is in this where the Virgin Mary is seen as the collection point for "sinners" like himself. The Virginal condition of Mary is set against how Stephen has frequented brothels and succumbed to the temptation of the flesh. The call for "interceding" is one in which Stephen realizes that his transgressions have been an affront to the divine. Calling out to the Virgin mother is a way for Stephen to be delivered into the realm of redemption from a domain in which sin and transgression has been intrinsic to his identity. The call out to the Virgin Mary is one in which Stephen hopes to be redeemed from his mundane appetites and enter a domain that is transcendent from that which is contingent.