"Marriage is intended to be a union based on the absolute."

Can you explain and back up this claim? Considering that polygamy is common worldwide, and even when monogamy is the norm many cultures have concubines and such, I question to what extent marriage is based on some absolute and to what extent you are taking the common christian additions to the general cultural practice. Also, I just don't know what you mean by the phrase, as it seems nebulous to me.