I'm writing a speech on using symbols, and I've just made the statement that you should generally stick with one, maybe two, symbols that span the story (smaller symbols that arise and fade quickly don't apply to this limit so much).
I now have to back my statement up. I know why you don't want too many symbols in a novel, but I'm having trouble articulating the exact reason. I feel it isn't just that the reader might become confused (though that could be part of it).
When I say 'symbol,' I'm speaking of a large symbol, something that spans the majority of the novel and plays a large part. Think the One Ring in LotR. It wouldn't be quite so strong if Frodo had to also destroy a jacket and five pebbles, but I can't quite say why.
Can anyone tell me the main reason you don't want too many symbols in a novel?