[the phantom]

I'm going to explain Tolkien's use of three and seven in a completely non-Tolkien, non-symbolic, non-anything way...

If you want something to be rare, three is a good number to pick. Having only one or two of something is too rare, but four is starting to be quite a few. Three is just right.

And seven- well, if you want only a few of something but not too few, and if you want several but not too many, a number between six and nine would work the best (because once you get to ten you are in double digits, which is too many, where as five is still too close to three). So which number do you pick- six, seven, eight, or nine? Well, knock the first and last off to get closer to the middle and you are left with seven and eight. Now, which of those numbers is a sexier, more appealing number?

I think we'd all agree that seven is the way to go.