There's a joke I heard in the UK... a man is complaining that "I can drink a glass of whisky, and that doesn't make me a whisky drinker; smoke one cigarette, without then always being considered a smoker. But suck one cock..."

Is Emily's view that bisexuality is not a real phenomenon, or that if it is, it precludes monogamy?

The man is question IS in fact cheating on his fiancee and is not being monagamous. Moreover, he has not been up front with his fianceee that he's bi. If he was, she could then decide if she was OK with that, but she wasn't the one writing to Prudie for advice. The main issue is that it appears he may at some point decide to have his penis surgically turned into a vagina, and his fiancee certainly deserves to know that.

Not disputing that he is behaving badly, or the wisdom/decency of disclosure. Just asking a specific question, since there does seem to be a commonplace implication (widespread in the culture) that if a man touches another man, he is therefore gay, irrespective of what else happens in his life.

It seems to me that the only determining factor regarding bisexuality or homosexuality is simply the assertion of gayness. As far as I know, there are no tests nor any scientific basis for such a claim. So the word "gay" or "lesbian" is therefore purely subjective. Anyone can claim to be gay or that they have never been gay. No way to verify, so what difference does it make if the future groom admits anything. How can he tell her he was bisexual when in an instant, he can become heterosexual again?

Well there is that whole sticking point of honesty and monogamy... So it matters not to you if your partners genitalia haven't been where they claimed it was?

Well, at least in common parlance, a person who has sex with partners of both genders is bisexual. But surely the more important points are a. he is cheating on his fiancee, and b. he is possibly transsexual. I would certainly hope that my friends would fill me in on something like this well before I got down the aisle.

I did not read that as him cheating on her now. I read that as his past is such, but he is turning his back on who he really is (his past) to pretend to be heterosexual. Now, you can easily debate whether his previous feelings that he should be a woman should be disclosed, but I don't see how you can say he is cheating based upon the letter.

The letter read: "I want to be a supportive friend, especially since his family may or may not accept his sexuality, but there is a catch. He has a girlfriend, who seems to be completely in the dark about all of his "extracurricular" activities. I've mentioned my discomfort with this state of affairs, but this only elicits vague promises that he will have an honest conversation about this with her "one day." Lately, he has assured me that he is done with "that life" and that he is perfectly happy with his girlfriend."

So that, to me, seems like the guy has been participating in cross-dressing and affairs with men since he's been dating the girlfriend.

phunkjnky, I'm not talking about homosexual "behavior." I'm talking about verification. In other words, we only have their "word" that they are bi or gay? When it becomes legally advantageous to be gay, a whole lot more people WILL become gay. It's as easy as saying "I'm gay." Regardless of actual history, gayness is simply an verbal assertion.

He says the following,

A very dear friend of mine seems to be going through a sexual identity crisis. He has dabbled in cross-dressing, sexual relationships with other men, and has even experimented a bit with female hormones. I want to be a supportive friend, especially since his family may or may not accept his sexuality, but there is a catch. He has a girlfriend, who seems to be completely in the dark about all of his "extracurricular" activities. I've mentioned my discomfort with this state of affairs, but this only elicits vague promises that he will have an honest conversation about this with her "one day." Lately, he has assured me that he is done with "that life" and that he is perfectly happy with his girlfriend. But I'm so afraid that he's turning his back on his own sexuality and settling for a life of miserable conformity. Now that he and his girlfriend are getting married, the stakes are even higher. Please, Prudie, what should I do? Should I tell the girl what I know about her fiancé? We live quite far apart, so a face-to-face chat is impossible. I hate the thought of devastating this sweet girl, but I'm also consumed with guilt at the thought of keeping her in the dark. Is action a moral imperative, or an unforgivable interference in another person's life?

If you notice, she does say that he HAS dabbled in those types of activities not that he is currently doing so. If he has cheated on the girlfriend while she is around then that would be a wholly separate issue than what this letter is about. She is worried that he is truly the crossdresser who likes men, but that he is pretending to be normal. If he continued to cheat or did so while he had a girlfriend, then it would make more sense to also say that he has cheated on her. She did not. Finally, the "extracurricular" activities is likely to refer to fact that he has hidden these activities from his family and now his girlfriend, not that they are what he is doing now. There is some ambiguity in the letter and you may be right, but an ambiguity works against you since you are the one asserting that he is cheating.