In the next place, since venial and mortal sins differ in respect of the debt of punishment, we must consider them. First, we shall consider venial sin as compared with mortal sin; secondly, we shall consider venial sin in itself.
Under the first head there are six points of inquiry:
(1) Whether venial sin is fittingly condivided with mortal sin?
(2) Whether they differ generically?
(3) Whether venial sin is a disposition to mortal sin?
(4) Whether a venial sin can become mortal?
(5) Whether a venial sin can become mortal by reason of an aggravating circumstance?
(6) Whether a mortal sin can become venial?