We all have it so easy. Our lack of technology keeps us from having to confront difficulties in the way that lack of clothing kept our predecessors from the same. Let's talk about homosexuality, or since they've stolen the word pretty seriously, "gay"-ness. We'll establish a scale of gayness using two extreme points, and try to suss out points in-between to understand the concept. We'll stick with male homosexuality for illustrative convenience, but it can apply either way.
Defining Leftward Boundaries: Gayest Possible
Okay, so what's the gayest possible thing? Is it gayer to have gay sex with a consenting gay partner, or is it even gayer to have gay sex with a non-consenting partner? I'll say the latter, since your gayness is so extreme that you're willing to cross the bounds of consent (but I'd be willing to hear opposite arguments about how valuing consent makes you gayer than being willing to cross the boundaries). And is it gayer to have gay sex with one partner, or more than one? That's a trickier one, since it's relative preference--a guy who wants to sleep with a million guys at once is pretty gay, but maybe he's all about quantity rather than quality, so the guy who wants to focus his complete attention on the perfection of just one other guy could be actually gayer than the one who wanted to have a million guys at once. So the scale of ultimate gayness can't depend on quantity.
Is paying for the privilege of said gay sex gayer than getting it for free? Again, dicey. Someone who would pay a billion dollars for one ultimate gay encounter might seem, on the surface, to be gayer than someone who wants the encounter but who wouldn't be willing to pay, but what if the latter non-payer doesn't want to pay because he wants the sex to be from the heart (even the forcible sex, i.e., it's on the heart for his part, not the recipient's)? So paying or not paying can't be the deciding factor.
The gayest possible scenario on our graph, then, is having forcible gay sex with an unwilling partner. But then, does it become even gayer if the partner is himself not gay? Not just non-consent, but utter revulsion? Or does that make it less gay because it's wholly one-sided? I'll say yes, it has to be non-consensual but lifestyle-reciprocal, in order for it to be ultimately gay. And I'll ignore arguments that private gayness allows for more measured appreciation of gayness, and say instead that exhibitional gayness is more gay, because it creates more of a systematic impact. And bringing sociology into this, let's say it has to be a known gayness, so Googling "Famous gay men" brings up as the first search result...what the fuck, Rachel Maddow is on the top of the page I clicked? Yes, checking, I actually did type "famous gay men." Okay, I can see the argument to be made there, but I'm going to dismiss that out of hand and try again...okay, this time I'll use "world's most famous gay man." Singular. And Google says...omg, you assholes, great programming job, it's right back to the same page with Rachel Maddow. Giving up on new search terms, just going lower on the existing list...the next two links are all about gay "people," not men, so going down to the fourth one, I get a top ten list, and the gayest one on that is "Abraham Lincoln." Therefore, the gayest thing possible on Earth at this point in time is for a man to bring Abraham Lincoln to the future and rape him on webcam.
Defining Rightward Boundaries: Straightest Possible
By some lines of thought, the polar opposite of gayness should be celibacy, but even without bringing Catholics into this, we can see that's a mistake, since the sterility of celibacy is closer to the sterility of gayness than is the fruition of straightness. The rightward boundary seems easy, but it's actually not: to be farther away from gayness, the boundary has to be reproductive sex, not sterile, pleasure-only sex; it has to include an hourglass woman, not one who is skinny and/or athletic enough that she could be likened to a boy or tomboy or butch or tough-girl or whatever; it also has to not involve any non-optimal reproductive positions or non-reproductive foreplay like unto sodomy. That doesn't mean that male/female oral sex is in any way gay, anymore than consensual male/male oral sex is in any way straight, but non-reproductive sex, as the pervies of old knew, is an eensy bit closer to the other side of the scale than reproductive sex, since it's a step away from the reproductive-naturalness that enshrines the difference(s) we're discussing here.
And if we mix in Europeoid-influenced cultures, we bring in marriage, of course. Marriage, the family, the shared parental investment, the genetic union: the straightest possible act on Earth at this point is either joyful or joyless male/female deep-penetration doggystyle during ovulation, where the female is mature but under mid-twenties for optimal reproductive success. Joyful or lustful thoughts don't kill the example, since those might be chemically and/or sacrally related to creating a better environment for pregnancy and/or childbirth and/or child-rearing. The woman is full-hipped and full-breasted, with adequate fat reserves, and she is thinking about hip angles for sperm routing; the man is thinking about his future progeny and/or his undying love for the woman's currently vital physical form, and they are in privacy, but with a strong family and national network waiting just outside who knows what they are doing and is ready to lend support to the pregnant woman and, later, the baby, and to respect and protect the inviolability of the couple's union, but equally ready to dissolve the union if it gets too dangerously pleasure-focused.
Okay, we have our boundaries. Somewhere slightly to the right of "time traveling madman raping Abraham Lincoln on Youtube" is "Elton John's afterparty," and somewhere further to the right of that is "Tim Cook's date night with his significant other" (you see how my earlier Google searching paid off after all?), and then nearby, but further still to the right, is "desperate prison rape," and even further is "WW1 Army dude jerking his friend off in a foxhole when they haven't seen a woman or had privacy in years and think they're dying tomorrow." Still on the "gay" side, but not as gay as a man inventing a time machine to rape Abraham Lincoln because he so desperately needs to.
Somewhere to the left of "maximally reproductive sex with hetero life-partner" is "only having sex when she's not ovulating so we don't have a kid/more kids," and to the left of that is "condoms and/or pills in hopes of guaranteeing nothing ever comes of sex but fleshy sterile pleasures," and somewhere around there also is "male/female anal," and further to the left or is "femdom" or "strap-ons," which, although utterly gay, are not necessarily technically gay, if it is 100% male/female interaction both in physical expression and in the last extremes of chemical and psychospiritual nuance within the participants' heads and/or bodies.
Is there an actual middle point, though? Is "zero" an impossibility? Can anything be sexual without being either gay or straight, even to some tiny degree kelvin? Yes indeed; try this: abandoned infant grows up on an island, never meets another person, and one time has an amorphous dream during which he ejaculates, feeling desirous and feeling pleasure but never knowing why. He never knows that he has a sex, that there are other sexes, or anything else--he doesn't make a pretend-wife out of coconuts, he doesn't find himself attractive in the reflection in the lake, he doesn't think there are other things similar to him anywhere in all of existence, and he dies never being rescued by civilization, never having a second sexual dream, never giving it much though. That is our zero point.
This is all just setup for the real questions, with which we'll continue soon.