The other posters have hit the nail on the head. Just because something occurs “naturally” doesn’t mean that it’s “natural”, strictly speaking. Down’s Syndrome occurs naturally, but it’s not “natural” – it’s a genetic defect, that we’re right in trying to eliminate. (Granted, there are many moral objections to which methods are permissible, but that’s beside the point.)
Naturally, the olfactory system is used for smelling. Can you receive nutrition through the nasal cavity? Sure! But that’s not “natural” - it’s a deviation from the norm, or “abnormal”. Naturally, the digestive system is used for digestion and the reproductive system is used for…wait for it…reproduction. Big surprise. To use our natural systems in ways they’re not designed to operate is to
mis-use the systems. It’s not unlike bulimia (or the Roman vomitoriums of old) - the proponents want to use the digestive system to give you the pleasure of eating but without the nutrition. It’s rightly condemned, because it’s not the function for which the digestive system was designed. Similarly, using the reproductive system (combined with segments of the digestive tract) in a way for which they’re not designed is to **mis-**use them. It’s rightly called “unnatural”, even if there are naturally occurring disorders which pre-dispose the adherents to the contrary.
Need an atheist to say it? How about this:
Sigmund Freud, who had little sympathy for religion of any kind, wrote: “. . . it is a characteristic common to all the perversions that in them reproduction as an aim is put aside. This is actually the criterion by which we judge whether a sexual activity is perverse - if it departs from reproduction in its aims and pursues the attainment of gratification independently… Everything that… serves the pursuit of gratification alone is called by the unhonored title of ‘perversion’ and as such is despised.”
Part of what you need to understand is the difference between nature and Natural Law (which is not necessarily religion-based, BTW). Natural Law describes how humans naturally and properly interact, as governed by reason and morals. Nature describes the state in which we find things
without reason or morals. Be clear on your terms; Natural Law condemns homosexual acts, while nature simply shows what happens to animals/plants divorced from reason/morality.
From the sound of it, your professor is either a subjectivist or a relativist. You might ask him if the Holocaust was “wrong”, or if it’s “wrong” to cheat on your wife. If you can establish that objective morality exists, Natural Law holds sway and the homosexual acts are rightly condemned. If he refuses objective morality, ask again if it’s okay to torture innocent children for fun – to be consistent, he has to say that there’s nothing “wrong” with it.
Further reading:
Homosexuality.
Hope that helps.
God Bless,
RyanL
