What is the best way to explain to a secular person why homosexuality is sinful?
Chastity is the most unpopular of the Christian virtues. There is no getting away from it; the Christian rule is, 'Either marriage, with complete faithfulness to your partner, or else total abstinence.' Now this is so difficult and so contrary to our instincts, that obviously either Christianity is wrong or our sexual instinct, as it now is, has gone wrong. One or the other. Of course, being a Christian, I think it is the instinct which has gone wrong. But I have other reasons for thinking so. The biological purpose of sex is children, just as the biological purpose of eating is to repair the body. Now if we eat whenever we feel inclined and just as much as we want, it is quite true most of us will eat too much: but not terrifically too much. One man may eat enough for two, but he does not eat enough for ten. The appetite goes a little beyond its biological purpose, but not enormously. But if a healthy young man indulged his sexual appetite whenever he felt inclined, and if each act produced a baby, then in ten years he might easily populate a small village. This appetite is in ludicrous and preposterous excess of its function. Or take it another way. You can get a large audience together for a strip-tease act - that is, to watch a girl undress on the stage. Now suppose you come to a country where you could fill a theatre by simply bringing a covered plate on to the stage and then slowly lifting the cover so as to let every one see, just before the lights went out, that it contained a mutton chop or a bit of bacon, would you not think that in that country something had gone wrong with the appetite for food? And would not anyone who had grown up in a different world think there was something equally queer about the state of the sex instinct among us?
In order for someone to be convinced by you, you have to at least share the same discourse and terminology. If the secular person you are talking to embraces the concepts of "sinful" etc. to begin with, you can go further (then, they are not so secular already). If not, you speak two different languages, and I would not go on waste both of your time.What is the best way to explain to a secular person why homosexuality is sinful?
I don't think your first point will get very far with someone who denies the existence of God.I think you gotta do two things. first you can explain that it doesn't work biologically. and why it does not fit the best (in my opinion) definition of love, which is to do to the highest good of the other at the sacrifice of the self. so if God defines sex as between man and woman in marriage, if one truly loves another man, he will not have sex with him and struggle against those temptations.
and I think we should always remind them that homosexuality, although more accepted, is not a worse sin than any other sin. it seems that modern TV Christianity there are three major sins: homosexuality, abortion, and reading stuff like Harry Potter or the Da Vinci Code, and you can fudge on divorce, making millions on people's donations, etc. I think nowadays they must be aware that homosexuals are not a worse sinner than a heterosexual, but someone with differing struggles.
I don't think your first point will get very far with someone who denies the existence of God.
I can think of intellectual approaches - but most people, not really being interested in intellectual explanations of a worldview, won't hang around for them.
I don't think you can define or explain sin in a secular context.
Begging your pardon, Ortho, but studies can be produced "proving" nearly anything at all. Many studies are driven by the agenda of the people funding them to produce the results they want to see. It would be one of the weakest and most easily countered points.
Damaris touched on a much stronger point and Jedi's linked thesis is outstanding. (I'm not finished with it yet, but its even-handed treatment of the people defending immorality makes it impossible for them to object that that is not how they see and present the case.)
I don't think your first point will get very far with someone who denies the existence of God.
Your second point is quite right and helpful. I would note the reason we hear so much about those particular sins, though, in all fairness to modern Christians - the modern, and mostly successful effort, to deny that they are sins at all.