1. Natural law “Nature tells us”
2. Jesus’ definition, quoting OT word for word “The Bible tells us”
3. “Culture tells us” This is where PC(USA) and the rest of "Mainline Protestants" live. The resolution I voted against at a meeting of the Presbytery of Boston [the local council of my denominations's churches] in Easton, Mass about a year ago even encoded culture’s inevitable shift, by saying PC(USA) ministers could perform same sex ceremonies where permitted by law. The law has changed since that meeting!
I suppose position #4 might be personal revulsion “My gut tells me it’s wrong” Where does the revulsion come from? Natural Law? Or from cultural attitudes, gutter-slurs, and fear of the other? If the latter, then #4 is more similar to #3. That’s why I reject #3 and #4, while recognizing the wisdom and usefulness of the other two, primarily #2.