Sunstone said:
Is there a factor common to all religions? The only one I can think of that might fit the bill is that nearly all religions involve some sort of ritual (even if they don't call it ritual).
Nope, that one won't do either. My religion is about as ritual free as it gets. Certainly we're not sacerdotal.
Yet, there are things that involve ritual which are not religions (marriages, for instance, involve ritual).
Uh, the marriage vow consists of repeating one rather short sentence. That's a pretty minimalist ritual, if one would even call it ritual at all.
But you do mention one thing religions do have in common -- they do define certain parameters for marriage. Other commonalities are funeral procedures, dietary laws, and often matters of inheritance.
So that characteristic of religions is not defining in and of itself. But what do you think? What do all religions have in common?
The Golden Rule, most likely.
Basic morality such as be truthful, honest, generous, cheerful, kind to others, etc. Help those in need.