If we are going to discuss marriage, then we should have a go a defining what marriage is before deciding on who might take part. Defining marriage should, at the very least, seek to define marriage. It is no good arguing about whether one might marry one person or two, whether it is okay to marry someone of the same sex or whether it is somehow immoral to exclude a coupling based on age, gender or quantity if one does not actually talk about what it is that unites someone in marriage. There are at least three ways of thinking about the actual relationship between people. First, and most popular presently, is…