Venial and mortal sins can only be distinguished when the motive and intent of the sinning person are considered. According to Abelard, for an act to carry any guilt with it three factors must be present. Consent we give to an evil suggestion. The evil deed itself. Devils can make suggestions from outside our minds, but this is not sinful without our consent.
Right action is only meritoriously good when it is accompanied by good intention.
However, to add good intention to right action is not of double worth. No action is right in and of itself. It is only truly right when proper intention is present. He does point out that sin comes in more than one package. Although the stoning of Stephen was a sin, it was not imputed to his executioners as sin because they were of a good, though misinformed, intention.