A marriage is distinct from, but cannot exist without the parties to it. Pro-creation is not a condition of marriage.
A marriage is both a collective of substances and a state (in philosophical terms, an accident) with a specific dependence on both parties to it. It is distinct from the substance of the individuals so joined.
Nevertheless, marriage is not a relational accident. Relational accidents (e.g. a dance, a conversation, a kiss) can be described as existing in their own right, with qualities and changes being completely un-related to the properties of the individuals involved. The state of being a wife, husband, a brother or an uncle *cannot be so*. They are not gender-neutral terms. Such states are sometimes described as ‘Cambridge relations’ (Mulligan and Smith 1986).
Comparatives (e.g. ‘is longer than’, ‘is faster than’) share a common characteristic with these ‘Cambridge relations’. As Barry Smith says of both in ‘Objects and Their Environments: From Aristotle to Ecological Ontology’: ‘They exist not as something extra, but only in reflection of certain special sorts of demarcation which are imposed upon the underlying bearers or upon their non-relational accidents.’
We may then ask how the demarcations are set for such relations. Why can’t a mother-in-law be male? Why can’t a great-uncle be female?
If you do, also ask why the comparative ‘is longer than’ can only relate the length of two objects, and not the area. It is the property of ‘longer than’ that predicates and imposes the demarcation of length, rather than area, on the two substances under comparison. Few would challenge that.
Yet, it is the same with these ‘Cambridge relations’. The legal context of all of the affinities involved imposes demarcations on the underlying bearers or their non-relational accidents. In the case of marriage, this includes gender.
This demarcation is only contested by gay and bisexual pressure groups as it relates to sexual orientation. They challenge demarcations on no other basis. It is therefore an unjustified exemption to exclude a specific group from the existing gender demarcations imposed on the parties to a marriage.
While pro-creation is not a requirement of marriage, it should certainly not be a ground for divorce. If a woman falls pregnant unexpectedly by her husband, she has a right for this unplanned event not to be treated as a matrimonial cause for divorce.
Conversely, a married man has the right to expect that the children born of his wife (those to whom he extends nurture as a father) are actually his. If they are found to be otherwise, it is a ground for divorce. These issues arising from the interaction of two genders are part of the reality of marriage.
How do we continue to legally define adultery as a ground of divorce, but in a genderless way? Heterosexual sex triggers a whole range of potential legal consequences regarding consent, legitimacy of offspring and parental responsibility. These are issues that current marriage laws protect. The root-and-branch removal of gender as irrelevant and non-existent in marriage makes the above-mentioned outcomes meaningless to marriage.
This approach is already is being applied to UK birth certificates. They no longer reflect the male biological parentage of the child, but the partner of the biological mother at the time of birth. Hereditary causes of birth defects, family illnesses and death are no longer traceable by authorities in these cases.
The similar attempt to re-define marriage without regard to gender only serves the special interest of one group. Yet, it causes marriage to cease to correspond to and address the realities of marriage.
Some equivalences are valid. On the basis of the foregoing, gay marriage is not. We might as well change the laws of every sport imaginable to ensure they all field 11 players a side, thereby claiming that this would achieve perfect equality.