ideosphere

(Side note. I just made this up. If the concept of ideosphere didn't exist outside my imagination, it surely does now. That's memetics for you.)

PS (thanks to pseudo_intellectual) I've read Hofstadter so it was actually a case of remembering; the meme was only passed on.

The realm of memetic evolution, as the biosphere is the realm of biological evolution. The entire memetic ecology. (Sorry rp, but Douglas Hofstadter beat you to the punch and coined this term.) The health of an ideosphere can be measured by its memetic diversity.

Current meme theory sees the ideosphere as our model for the physical world. Thus we see horses in the physical world, and create ideas of horses in our minds. People's conceptions of horses will differ because not everybody will use the same memes when building a model of a horse.

Plato, on the other hand, saw the real world as simply the shadows cast by 'the world of ideas'. There was one idea for a horse, and this idea was a kind of blueprint; it contained everything that could possibly be perceived about a horse. Then the differences between how people saw horses were due to differences in the interpretation of this one idea, not differences in the actual idea.