Back from class and procrastinating on homework by doing an analysis of numbers in literature and mythology as perceived by myself.
1 seems to be the obvious one. One. Only one. The one and only. It's something unique and/or special.
2 seems to be used a lot for pairing and comparing. Often there are two things that are juxtaposed. Combinations of two often show either some sort of collaboration or some sort of competition, or "oppositeness". The Two Lamps are like the two poles of Arda the flat. The Two Trees have a bit of both relationships; one one hand, they are paired together, but on the other hand they are given opposite characteristics (gold vs silver). Gondor/Arnor - same story. This is also true for the making of choices and family relationships. You have Hurin/Huor, Turin/Tuor, Elrond/Elros - which are paired and compared, even if not explicitly - and they are connected to each other so strongly with that comparison that sometimes it's hard to think about one without thinking about the other.
3 appears to be used when you want to show equally valid components without necessarily pitting them against each other. Three Houses of Edain and of Elves are good examples. Alternatively, it just seems like an appealing number for things that are rare but not unique - Silmarils, Elven Rings. This might be a matter of taste that was just conditioned into us by past literature, and it keeps getting recycled over and over again as new literature is made.
4 is odd, I think, because though it seems "stable" mathematically (perfect square and all), it tends to fall apart (at least in my mind) into 2 and 2 when a quartet appears in literature. The thing about even numbers is that perhaps I automatically want to pair (which is why 3 seems to be associated with a more stable relationship - you can't split it into independent pairs). But I don't think it's just me. Four hobbits go with the Fellowship, and they are subdivided early on in their travels into the Frodo-Sam pair and the Merry-Pippin pair. Four just doesn't seem to be able to hold together.
Harry Potter has great examples for both 4 and 3. They have 4 Houses, but instead of being portrayed as equally valid they are split into "Gryffindor vs Slytherin" and "the amity (and relative unimportance) of Ravenclaw and Hufflepuff". On the other hand, the Tale of Three Brothers in the 7th book shows three different approaches, without necessarily showing competition between them, and without grouping anything.
I wonder if there is any grouping of four that does not fall apart. I suppose in HP itself there are the four friends of the parental generation, but that relationship is skewed and unequal to begin with; there's one person who sticks out from the start. In the natural world you have the four corners of the world (and in some places the four elements), which should technically be representative of stable quartets, but I can't think of any examples at the moment. The Greeks even had just three winds, ignoring the East Wind completely, if I remember correctly. Thoughts?
There's something appealing about small odd numbers. 5, 7, 9 are, in my opinion, chosen less for their own merit than as a means of avoiding the more boring 6 and 8. There's nothing wrong with either of them, but odd numbers just seem more satisfactory. (Compare the number of trilogies and 7-book series to the number of series with a different number of books. 4 and 5 occur occasionally, but I've yet to see a 6 or an 8). You can't group things into equal portions with 5 and 7, and 9 is broken into a 3 of 3s. These numbers seem to be more like 3 and less like 4, though they still could be broken down into uneven segments.
It's interesting that if a larger number is of a homogeneous thing, it's more stable, but if there are differences than it breaks apart into smaller groups. I've got no problem with 9 Nazgul, but some area of my brain feels the need to subdivide the Fellowship into smaller groups. Gandalf of course has a group all for himself. The Men seem to be paired and even have a subtle competition going on. Perhaps it's in the way they are described (e.g. "Boromir was wider, but Aragorn was slightly taller" (paraphrased)), or perhaps it's just me; when I read LOTR as a kid, Aragorn was my favourite character, and I was indignant any slight to him. I would get indignant when the book said Boromir killed more orcs than Aragorn. I guess I felt the need to justify my favourite character, and any equal seemed like a rival. But moving on. Legolas and Gimli are paired by virtue of being the "weird foreign people/races", and then they develop their unusual relationship, and basically by Lorien they are a character couple. That leaves the four hobbits as a group - but as I mentioned before, that number seems to fall apart too.
Perhaps a lot of this is our tendency to categorize things. Perhaps it's not that we (or authors) choose to group things a certain way to show something with the use of numbers, but rather the reason we see something in numbers in the first place is because of the relationships in these pre-existing categories; we perceive first, and count later, but then we think it's the number that influences what we perceive. A lot of it has to do with conditioning - you read a book where the number 3 holds some significance, and you generalize that feeling to other trios.
Well, that was food for thought, but thoughts for food are hardly as good of an offer. Lunch!