Hey grace, marriage is a religious ceremony created by religion of course. Marriage is the bringing of two people together. It is not non religious because it was created by religion. Even if people can get legally married without religion that does not mean it is not religious. Marriage is still a ceremony created by religion( also I'm saying religion not Christianity). Another example of this situation is how religious holidays get manipulated into non religious holidays, like Christmas. Christmas is a religious holiday( first pagan then christian)in the Christian view as the birth of Jesus, but was then manipulated by people who don't believe in religions into a secular day involving goodness and presents. Marriage is just like this because marriage is a religious holiday created by religion, not just Christianity.