Teleology
The telos of heterosexual intercourse is life and the perpetuation of families, nations, and our species.
What is the telos of homosexual relations?
Neither hetero or homo sexual relationships have anything to do with marriage. They are a commitment to a financial contract. A piece of paper and vows before God can be understood without taking them in front of anyone and did for a long time before the institution of marriage was determined and was many times set up by families for financial or control gains, not for what the public considers today.
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