Immanuel Kant, a German Philosopher invented “Kantian Ethics”, an enemy of Utjlitarianism. His theory involved two questions to decide whether a decision was morally correct; one, Can I rationally will that everyone act as I propose to act? If the answer is no, then we must not perform the action.
Two, does my action respect the goals of human beings rather than merely using them for my own purposes? Again, if the answer is no, then we must not perform the action. If either one was negated there isn’t even purpose in seeking the second question. 0n the topic of same sex marriage a supporter of Kantianism would argue against it, Kant saw sex as an animalistic desire of self-preservation and enjoymentr.
He thought sexual intercourse was degrading because it reduces humans to an object of pleasure, he in fact thought of masturbation as worse than suicide, putting a person‘s status below that of an animal. With sex the only means that come from it that Kant would agree with is that of producing offspring, otherwise it‘s merely the same as masturbation, and there are no offspring produced in a same- sex marriage, so I believe he would argue against in with the argument of self-preservation, his first question is can everyone act this way? And the answer is no, if everyone were in a same sex marriage, our species would only last this last generation, And the second question worries about doing the act for yourself verse humanity, and in a civil-union it’s quite obviously for yourself and the only thing you get out of it is tax breaks and peace of mind.
Kantianism is against sameesex marriage for it clashes with both of his questions that allow an act to be done.