I consider that a man's brain originally is like a little empty attic, and you stock it with such furnature as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skilful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.
-Sherlock Holmes, A Study in Scarlet
I'll bite: how am I supposed to judge (or predict) the usefulness of facts when I first see them, in time to avoid storing the useless ones?
I think the closest we get to this is that every time we remember something, we also edit that memory, thus (if we are rational enough) tossing out the useless or unreliable parts or at least flagging them as such. If this faculty worked better I might find it a convincing argument for "intelligent design," but the real thing, like so much else in human beings, is so haphazard that it reinforces my lack of belief in that idea.
Here's the new thread for posting quotes, with the usual rules: