What does a couple have to validly promise each other, explicitly or implicitly, in order for those promises, when appropriately ratified by authority, to give rise to a marriage?
This is a hard question as to the specifics. But we can at least give a start of a functional characterization:
- Marriage vows are that complex of binding commitments that in fact makes it prima facie permissible for a couple to engage in intercourse.
Of course, this account can only have plausibility if uncommitted sex is wrong. I think that prior to the 20th century in the West, this functional characterization would have been seen as quite plausible, and I am still inclined to think it is correct.
A functional characterization is not, of course, a definition. Thus someone who disagrees with this characterization can still be talking about the very same thing when using the words "marriage vows" as someone who accepts this characterization.