What Constitutes a Marriage?

Questions about what constitutes a marriage, at what point God considers a committed relationship to be a marriage, whether the freedom to pursue marriage is a natural right (and what restrictions would be inappropriate), and how to decline an invitation to an unbiblical wedding.

• What constitutes a marriage?
• At what point does God consider a committed relationship to be “marriage”?
• Is the freedom to pursue marriage a natural human right, and are there any any inappropriate restrictions that should not be placed on marriage?
• Should I explain my reason for declining an invitation to a marriage ceremony that doesn’t reflect the biblical order or just address it when asked?