As I am writing this, same sex marriage is legal in the United States and in 2025 the supreme court declined to revisit the gay marriage decision. But as Roe v Wade was overturned, it is wise to consider that there is no such thing as settled law. While I am a divorced straight man, I am a staunch defender of same-sex marriage on the grounds that everyone should have the right to make bad decisions that cost them half their stuff.
As opponents of same-sex marriage tend to reuse the same fallacious arguments, I’ll do a brief recap of them here in anticipation of future fights. The first stock argument is that marriage between a single man and woman is a tradition. This is a fallacious appeal to tradition. The mere fact that something is a tradition does not show that it is right or correct. To use the usual counterexample, slavery was (and is in some places) a well-established tradition, yet this does not justify it. But as some opponents of same sex-marriage might like slavery, there is also the example of murder, which is something humans have been doing a long time.
A second fallacious argument is that marriage between a man and a woman is what most people do, thus it is correct. In other words, it is a common practice and thus is right. Obviously enough, this is a fallacious appeal to common practice. There are, obviously enough, many bad practices that are common (like lying), but being common does not make them good.
A third common fallacious argument is that most people believe that marriage should be between a man and woman. Even if it is assumed this is true, this would still seem to be a fallacious appeal to belief. After all, the mere fact that most people believe something (like the earth being believed to be the center of the solar system) does not prove that it is true.
Now that the easy to dismiss fallacious arguments are out of the way, I can look at some of the other arguments that have been presented against same-sex marriage.
One common argument is an appeal to religion, specifically Christianity (at least the versions that forbid polygamy). The argument typically goes that since God married Adam to Eve; this defines marriage in the biblical sense. Those with clever wits often put it more rhetorically by saying that it was “Adam and Eve, not Adam and Steve.” Since marriage is defined by the Christian faith as between one man and one woman that is what the law should be. As might be imagined, there are many problems with this.
One obvious legal problem is that to the degree those using this argument claims that it is based on a specific faith, they are in danger of violating the first amendment of the United State constitution, namely the bit that “congress shall make no law respecting an establishment of religion or prohibiting the free exercise thereof.” While I am not a constitutional lawyer, I would suspect that a plausible case could be made that creating a law explicitly based on a religion does involve the establishment of a religion. But the Supreme Court might see things otherwise.
In addition to the possible legal problems, there is also the moral concern about imposing a specific faith’s values upon the population. This would seem to be a clear and direct violation of religious liberty and thus would seem to be morally unacceptable.
A second obvious problem is that basing the law on a religious view would seem to require that this view be established as correct. After all, if it is claimed that marriage is such that it can only between a man and a woman because of what God wants, then it needs to be established that God exists and that this is what God, in fact, wants. Otherwise, the law would have no established foundation and would be as sensible as basing a law on a myth or fictional tale. That said, law is all make-believe anyway, so perhaps this would be fine.
Naturally, if it can be shown that marriage is between one man and one woman as a matter of metaphysical necessity, then that would nicely establish the foundation of a law banning same-sex marriage. In fact, it would show that no such law would be needed since no one else could, in fact, be married. To use analogy, we do not need laws that ban people from driving their cars faster than the speed of light—they simply cannot do this because of the nature of reality.
There are, of course, non-religious arguments for eliminating same sex-marriage. A common argument is that this must be done to protect the sanctity of marriage. The idea seems to be that allowing same-sex marriage is harmful to marriage (and presumably to the married) and thus, on the principle of preventing harm, same-sex marriage should be outlawed.
One obvious point of concern is whether allowing same sex-marriage harms marriage and heterosexual couples. While, of course, it might upset them that people are doing something they do not like (getting married), that is not sufficient justification. What would be needed would be objective evidence that same sex-marriage does enough harm to marriage and married couples to warrant forbidding same sex-marriage. The evidence for this seems to be, obviously enough, sorely lacking and the burden of proof rests on those who would make an imposition on the liberty of others to show that such an imposition is warranted. We have had same-sex marriage for quite some time and all the dire predictions have failed to come to pass. This will, obviously, not stop opponents of same-sex marriage from simply lying or making up new harms.
Intuitively, same-sex marriage did not harm marriage or married couples. After all, it is difficult to imagine what sort of damage could be inflicted. Did married couples love each other less? Were there be more cases of domestic violence or adultery? Were married parents be suddenly more inclined to abuse their children? None of this seems to have arisen from the legalization of same sex marriage.
But suppose it is assumed that marriage simply must be protected. If this is taken seriously, then it would certainly seem to follow that it would need to be legally protected from whatever might damage its sanctity. By analogy, laws to protect people from murder are not just limited to, for example, making it illegal to murder someone with aluminum baseball bat. Rather, it is the murder that matters. The same should apply to marriage: if marriage must be protected by making it between one man and one woman, then surely it must also be protected against whatever would damage its sanctity. As such, it would seem equally reasonable to ban marriages involving any sort of person whose actions or nature might do damage to the sanctity of a marriage.
Intuitively, allowing immoral people to marry would seem to damage the sanctity of marriage. As such, people would need to establish their moral goodness before marriage and presumably any straying from the path of virtue (such as by having an affair or otherwise failing in their vows) would result in the marriage being suspended or even nullified. Naturally enough, people who intend to get married in the hopes of financial gain, from lust, or for any reason that would sully the sanctity of marriage would need to be prevented from doing so. If the self-proclaimed defenders of the sanctity of marriage were content to merely undo same-sex marriage, one might suspect that they were acting from mere prejudice against same sex couples rather than by a sincere desire to protect marriage. There is little difference between telling same-sex couples that they should not marry because marriage must be protected and telling anyone who would allegedly violate the sanctity of marriage that they cannot marry. As such, more general restrictions on who can get married (such as people who are not morally good or who are not marrying purely from love) would seem no more (or less) unjust that preventing same sex marriage.
Naturally, being a person with a social conscience and a professional ethicist, I would be willing to accept the position of Marriage Czar and head up the Sanctity Defense Agency to ensure that marriage remains eternally pure and unsullied. No doubt I would have to spend most of my time dissolving existing pseudo-marriages (starting with, one assumes, Donald Trump), but I am sure people would thank me in the end.
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