only become mortal when they contract some special malice from the circumstances. Fidelity to a simple promise binds under pain of venial sin, but when the promise is bilateral and the matter serious, as in espousals, it binds under grave sin and in justice.
4. From what has been said about mortal sin, it will be clear that a sin will be venial if anyone of the three conditions required for mortal sin be wanting.
5. Mortal sin may in certain circumstances become venial, and, on the contrary, venial sin may become mortal. The following paragraphs will make this clear:
(a) Mortal sin may become venial on account of an erroneous conscience which wrongly judges a grave sin to be only venial.
(b) The same may happen on account of imperfect advertence or imperfect consent to an act which in itself is gravely sinful. '
On the other hand, a venial sin may become mortal:
(a) On account of an erroneous conscience which falsely judges a venial sin to be mortal.
(b) On account of a gravely sinful intention with which a venial sin is committed, as when a lie is told in order to commit adultery.
(c) On account of the proximate danger to which one is exposed of committing grave sin, as when one reads a slightly indecent book, but foreseeing that it will be the proximate occasion of grave sin.
(d) On account of grave scandal caused by venial sin.
(e) When light matter coalesces and becomes grave by additions, as when one who is bound to fast frequently in the day takes small quantities of food, which are notable in the aggregate; or when a considerable amount of money is stolen in small thefts.
Although no mere multiplication of venial sins can ever amount to a mortal sin, yet venial sin frequently committed disposes the soul to commit mortal sin both directly and indirectly. Directly, by forming a habit which becomes stronger and stronger, continually requiring greater indulgence for its satisfaction, and finally leads to mortal sin. This is often seen in such sins as theft and lust. Indirectly, because venial sin familiarizes the soul with wrongdoing, lessens the fear of God in the soul, diminishes the fervour of charity, and causes God to withhold those more abundant graces which he would otherwise give, and which would preserve the soul from sin, but without which the soul falls grievously.
