Fr. Z's blog lists the ways we contribute to the sin of others, which also require our contrition and confession. There are many ways to participate in the sin of another person: 9 ways! You can be guilty of the sin committed by another: By counsel (to give advice, one’s opinion or instructions.) By command (to demand, to order, such as in the military.) By consent (to give permission, to approve, to agree to.) By provocation (to dare.) By praise or flattery (to cheer, to applaud, to commend.) By concealment (to hide the action, to cover-up.) By partaking (to take part, to participate.) By silence (by playing dumb, by remaining quiet.) By defense of the ill done (to justify, to argue in favour.) One can argue about how directly you must be involved to be guilty of the sin and also to incur the censure. [speaking of abortion] Paying? Driving? Urging? Working in the clinic? Etc. However, if you have any doubts about your own state of participation in such a thing, you should find a good, solid confessor and put the whole thing to him in the context of sacramental confession or internal forum discussion.