What is your evidence that natural law has never been found and is fictious?

@DavidGudeman: One can't prove a negative. If you want to challenge this, provide a positive.

@DavidGudeman The proponents of the concept of a “natural law” claim to derive it from the human nature. But the latter is not a result. It is an ongoing research project, in Europe at least since the days of Plato and Aristotle.

Obviously the OP should take from this exchange that moral realism has capable proponents like Smith's In Search of Moral Knowledge.

@keshlam, if you have no proof, you shouldn't say it as if you do.

@DavidGudeman They didn't say "is fictitious", they said "seems fictitious".

@DavidGudeman The general idea is that naturalists, researchers, etc... have always unconsciously ignored evidence of gay animals. Because they assumed it was unnatural, they explained it away as bad data or a dirty set of binoculars... . But they saw it a lot. So saying that opposite-sex pairings are the rule in nature has "never been found" is saying that we only thought we found it, but we've actually found the opposite.

Even if honosexuality hadn't been found in other animals, what would that mean? Neither has human-like language, but no one claims that makes it unnatural and wrong. Why couldn't homosexuality be a supreme human achievement rather than some kind of moral failing?

But human language is sinful and wrong! :-)

There are natural "laws". Life must eat (even if they can photosynthesize, they need raw materials to work from.) Actions have consequences. Sex sometimes causes reproduction, That sort of thing. But most of what gets defended as "natural law" is nothing of the sort; it is an attempt to argue against nature by presenting selected examples and ignoring counterexamples, and by claiming that things only have a single purpose.

@OwenReynolds, "natural law" is a technical term in philosophy; it doesn't just mean "law that comes naturally to people". In fact natural law always goes against nature. Why would you need law to tell you to do what comes naturally?

@keshlam "one can't prove a negative" - empirically, one can't prove a positive either. However, it is possible to provide evidence for either. Consider: "there is no flour in the pantry", evidence could be "I looked for flour in the pantry, and did not find any"

It only takes a few confirmed, repeatable instances to prove a positive; if it happens, it's possible (unless you misunderstood what happened). It's much harder to argue that if we haven't seen it yet, it won't occur. "I saw flour in the pantry" is hard to argue with; the others less so.

It is not only a moral law, contrary to the term "laws of nature" which means what is physically possible, the word "natural" can mean "common, normal, expected, ordinary". For example, it is physically possible for people to be born with a missing limb, it is not considered "common, normal, expected, or ordinary".

@Barmar I do not personally hold this position but the "unnaturalness" of homosexuality is most likely tied to the fact that homosexual acts of sex do not and cannot serve the purpose of reproduction. It is not about something being or not being found in nature, it's simply a statement that sexual acts should serve their primary biological purpose. This is also demonstrated by the fact that people who think homosexuality is unnatural tend to believe that heterosexual intercourse that doesn't lead to reproduction is immoral as well.

@Hrach Yes, that's their thinking. But their justification for declaring "primary biological purpose" is usually due to analogies to other animals, which turns out to be wrong. Who are they to declare that another purpose of the genitals is for pure pleasure?

@Barmar I don't know who "they" are in this case but a consistent argument can be made without using other animals. You can come to this conclusion if you either accept that the human body was created by a creator for a specific purpose, or that the evolutionary purpose of persistence and procreation is the supreme purpose of life. The latter is even objectively true from the point of view of evolutionary biology (there are no evolutionary mechanisms that strive to independently maximize pleasure or happiness). So I don't see any need for introducing other animals into the discussion.

@Hrach It's an extreme oversimplification to reduce natural selection to procreation. In social species, many "natural" activities serve purposes related to group cohesion, which has indirect impact on genetic advancement. See my comment to Batperson's answer regarding homosexuals serving a purpose in society.

@Barmar And what evolutionary purpose does group cohesion serve?

@Hrach In social species it's generally necessary to distinguish in-group (friends and family) from out-group (enemies). That's why they have group rituals (e.g. grooming in apes, dinner parties in humans).

@hrach Evolution doesn't have a purpose, but there are many obvious advantages to the survival of a population to be derived from group cohesion, from flocking and schooling to avoiding in-breeding. The survival of an individual is meaningless if there are no suitable mates available.

@Barmar Yes, and what is the purpose of being able to better distinguish friends and family from enemies? Reducing natural selection to the selection part is not in any way an oversimplification.

@Hrach You're basically asking "why is being a social species beneficial?" That's way too broad to answer in a comment.

But try reading something like "The Selfish Gene".

@Barmar All my recent questions in this thread have been rhetorical, I'm not asking you to explain the evolutionary benefits of social animals. As I said, the point is that reproduction is ultimately the "purpose" of evolution and since some people might have a problem with the word purpose, reproduction is ultimately the deciding factor. If you don't reproduce (whatever the reason for that might be) then your genetic makeup will quickly be removed from the gene pool. This is not an oversimplification, this is the very essence of natural selection.

Once you accept evolutionary persistence as your purpose, then anything that doesn't advance that goal can be classified as unnatural. Of course, there are absolutely evolutionary benefits to having homosexual individuals in your society otherwise homosexuality wouldn't be so widespread in nature. But that's why I am not arguing for this position. My only point was that one does not need to introduce other species into the discussion to talk about what is and isn't natural. That would indeed be an inconsistent and poor argument.

@Hrach If you want to think in terms of a "purpose" for evolution, it would have to go beyond merely the reproduction of some sort of genetic material. The purpose of continuous reproduction could easily have been fulfilled by bacteria for billions of years. Instead we have all these wonky trees and whales and tarsiers and mushrooms. If you try to assign a purpose to evolution it has to include diversity, not just successful reproduction.

@Hrach The general argument is that anything that helps children reach reproductive age and then mate serves the "purpose" of evolution. So people who don't themselves reproduce, but serve as nannies for those who do, are useful. This is one of the answers to why people continue to live into old age, even though they're no longer fertile and the children have left the roost: they often serve as midwives and babysitters.