I’m supposed to provide the hidden premise and counterexample for this statement:
Gay marriage should not be legalized because the definition of ‘marriage’ has always been understood to be a sacred union between a man and a woman.
This is my answer:
Hidden Premise: gay marriage is defined as marriage between same sex couples
Hidden Premise: Legalized marriage must follow the definition of marriage.
Counterexample: Some states recognized same sex marriages even though the definition of marriage is the same for all states.
Are my answers valid?
Answer by Jürgen Lawrenz
Not really. You missed the central issue altogether. Legal marriage is a social construct, originating in the dim history of mankind, that provides a male exclusive sexual access to a female for the sake of obliging that person to acknowledge the children of this union as his offspring, for whose nurture and welfare he is accordingly responsible.
The ‘sacred union’ is a subtext, arising from the religious foundation of society. Historically most societies lacked a police force or other means of ensuring that the marriage contract is not infringed. Accordingly religion functioned as a moral enforcer, which works as long as fear of the gods remains effective.
You should take note that divorce laws were historically grounded in the same principle. A man could be empowered to seek legal divorce if his marriage remained barren.
Obviously all these issues arose in male dominated societies. Love played little or no role in it. Marriages tended to be arranged by parents or authorities.
In societies with a measure of liberality, love itself may come to be institutionalised. E.g. in the 18-19th centuries, marriages increasingly became love matches. The ceremonial (religious) aspect remained largely unchanged, until in the second half of the 20th century, ‘free’ (civil) marriages increased and divorce laws changed to account for incompatibilities between the partners.
From all this you can see that homosexual marriages do not offend against any sacred principles except in societies that uphold the sanctity of marriage officially. They offend of course against the older principle that the purpose of marriage is to produce legitimate offspring. But in the modern world this principle has also become irrelevant.
So ‘love match’ is the one principle left. Under those criteria any society that does not prohibit extramarital sexual relations, and is not dominated by religious doctrines, has no leg to stand on if it prohibits a love match, irrespective of the sex of the partners.