Marriage...is the union of two people of different sexes with a view to the mutual possession of each other's sexual attributes for the duration of t… - Immanuel Kant

Act only according to that maxim by which you can at the same time will that it should become a universal law.

...[W]e must admit that... law must be valid, not merely for men, but for all rational creatures generally, not merely under certain contingent conditions or with exceptions, but with absolute necessity...

...[M]an and generally any rational being exists as an end in himself, not merely as a means to be arbitrarily used by this or that will, but in all his actions, whether they concern himself or other rational beings, must always be regarded at the same time as an end... [R]ational beings... are called persons, because their very nature points them out as ends in themselves, that is, as something which must not be used merely as means, and so far therefore restricts freedom of action (and is an object of respect).