On Reading Breaking the Spell - Ch1.2

Dennett puts forward his initial stab at a definition of religion as:

Social systems whose participants avow belief in a supernatural agent or agents whose approval is to be sought.

As he points out, this excludes some things that are generally considered to be religions (or at least, religious), and includes others that perhaps should not be:

What apparent grounds the widespread respect in which religions of all kinds are held is the sense that those who are religious are well intentioned, trying to lead morally good lives, earnest in their desire not to do evil, and to make amends for their transgressions.

He had just mentioned things such as satan worship and groups who feel they can summon and control supernatural beings (such as demons) for their own personal ends. These are the sorts of things he feels deserve to be left out of his definition of religion - presumably because he wants to try and capture what most people think of when they think 'religion', and also wants to analyse those that, as he states above, are based on trying to conform to some moral code of conduct.

There are, in contrast, a few 'congregations of one' which he feels fall outside his definition, but deserve to be included as 'honorary' religions.

I could hardly deny the existence of individuals who very sincerely and devoutly take themselves to be the lone communicants of what we might call private religions. Typically these people have considerable experience with one or more world religions and have chosen not to be joiners.

So, we have an initial cut at a definition of what he will talk about in the book, and already he's tearing it apart, trying to find where it doesn't fit. Indeed, even before he makes his first stab at it, he has said that nothing he defines will truly fit the bill. This dissection is a good thing, imho - it means that while he is going to talk about "religion" it isn't necessarily some fuzzy term meaning different things to different people - but he *is* allowing it to be a bit fuzzy sometimes and encompass some of those things that the rigorous definition does not explicitly include or exclude.

What other definitions of religion are there? Is even defining religion an exercise in futility because so many people think it has so many different meanings? Or is it good to put a stake in the ground, and use this to point out wha