Jim asks whether or not masturbation is a sin. Which is a good question, even in these days when objective right and wrong are so unpopular. Before the topic can be approached in its own right, a few misunderstandings need to be laid to rest.
First, "the sin of Onan" was not masturbation but coitus interuptus, a form of natural birth control. His sin was not pleasuring himself, or using birth control, but failing to do right by his dead brother and continue the family line (Gen 38:8-10). Thus we exhaust all possible references to masturbation in the Bible.
Second, the advice given to Jim by his pastor and advice I have heard given elsewhere, that as long as you masturbate "without lust," i.e. not thinking about someone, is crazy talk. I once heard a youth pastor tell her flock that as long as you thought about something non-sexual while doing it it was OK, and so she recommended thinking of shopping trolleys! This ignores the possibility that, "Sexual responses can become attached to formerly neutral stimuli by pairing them with masturbation." Simply put, you run a severe risk of developing a sexual orientation towards shopping trolleys (or whatever else you might be thinking of). This may have the consequence of inhibiting normal sexual expression at a later date and/or of making visits to the supermarket an uncomfortable experience.
Third, advice about masturbation is usually given to young men who also suffer from another issue related to their adolescant sex drive: "nocturnal emmissions," AKA wet dreams. Accordingly I have a heard a youth pastor teach that boys should avoid masturbation, which makes them lustful, and instead enjoy their wet dreams, which, while may be every bit as lustful, they cannot be held responsible for because they are only dreaming. However this in no way spares boys from their lustful desires but merely makes them prey to their subconscious which is likely even more depraved than their waking imaginations.
And so the question becomes, given that all the above are dead ends, how should we begin to construct a Christian ethic regarding masturbation? What do you think?