Are not the "body parts" sufficient? Is it not the joining of certain "body parts" and the natural result, that provides the biological foundation to marriage?How, exactly, are men and women different, other than body parts?
Appealing to biology is logical though.Appealing to tradition.
"Sense" that you wish to acknowledge, and doesn't undermine your position....no.You make no sense.
Perhaps you can answer the questions I posed.
If its the consensus of society that marriage is simply a union of two consenting adults, there's no need to prohibit any two person, consenting adult, union, including blood relatives. Why should it matter who marries who, or who can't marry who?
Your argument seems to be no restriction, except possible number of participants, among consenting adults.
If that is so, why bother licensing marriage at all?