Agreed. But Angra's point is that the definition of illness is also subjective; when we say that people with schizophrenia are ill because they have impaired cognitive functioning, we are essentially saying "impaired cognitive functioning is icky." There is much more consensus on that point than there is on gay sex being icky, but the foundation is no more absolute. Just as one could support calling schizophrenia an illness by saying people need to have accurate representations of reality in order to operate in day-to-day life, one could say homosexuality is an illness because it hinders the propagation of the species relative to heterosexuality. I disagree with the classification because there is an accepted definition of illness that does not encompass homosexuality, but that definition was arrived upon by consensus, not by empirical observation.
But it was a consensus which was arrived at through empirical observation. It wasn't just people randomly deciding something, it was a definition that was come up with after long experience of dealing with people with various potential things which could be classified as mental illnesses and determining what properly categorized them as distinct from other things. There's a reason that the consensus of the term is what it is.
1. Actually, an operational definition of "mental illness" is only arrived upon after studying many
mental illnesses, and working on such a definition. But that means they had a previous, already existent concept of mental illness. That is the concept I'm using, by the way. Whether the definition matches it is not the issue. Would you agree that, say, schizophrenia is a mental illness by the already existent concept, and that that was an objective matter?
2. Long before there was any definition of mental illness, there was a concept of mental illness, and more generally, a concept of illness that was applied to mental illnesses too. Even centuries ago, people would have been able to tell that someone was mentally ill, in many cases because it's obvious.
Would you agree that schizophrenia was an illness by the usual, intuitive concept of illness, before any definitions were given? Would you agree that whether psychosis was an illness was an objective matter, say, 300 years ago, and by the usual concept of "illness"? (even if they didn't know about schizophrenia in particular).
3. The definition of "mental illness" that you provide contains the condition that it causes an
impairment. Do you agree that there is objective impairment? Has someone given a definition of impairment, to use in the context of te "mental illness" definition? Or is it used intuitively? If it's used intuitively, do you agree that giving a definition is not required for objectivity, given that there is an objective fact of the matter as to whether, say, psychopathy causes an impairment?
4. Moreover, if we go by the definition
given in Wikipedia, one of the disjunctive conditions for mental illness is that it causes "an impaired ability to function in ordinary life (disability), and which is not developmentally or socially normative."
Does homosexuality cause said impaired ability?
Well, some people would say that it does, because it impairs the ability to enjoy romantic relations with to the opposite sex, and/or not to be sexually attracted to the same sex.
But you say it does not cause such impaired ability, right? (unless you reject the Wikipedia definition; if so, please provide a link to your definition of "mental illness" of choice)
So, you implicitly accept that there is an objective fact of the matter as to whether the ability to enjoy romantic relations with to the opposite sex, and/or not to be sexually attracted to the same sex, are abilities whose impairment impairs the ability "to function in ordinary life", and you hold that they are not.
Yet, you do not make that assessment based on a definition of "impaired ability to function in ordinary life", or a similar term, right?
You make your intuitive assessment, right? (else, please define "impaired ability", "impairment", or similar terms, and of course I will just make the same argument using whatever terms you define.). Other people deny it. But you do not reject objectivity on the matter, right? So, why do you reject objectivity on the moral issue?
5. Cancer is an illness, right? Do you agree there is objective illness? Do you think it's because there is some definition of illness? If so, what's the definition? If not, then why would definitions be needed for there to be objectivity?