A word can only serve to indicate that someone else may have a valuable idea—that is, some useful structure to be built inside the mind. Each new word only plants a seed: to make it grow, a listener's mind must find a way to build inside itself some structure that appears to work like the one in the mind from which it was “learned”.

Functional magnetic resonance imaging (fMRI)… can capture pictures of the brain in action. Researchers ask subjects to do something inside the machine—hum a tune, listen to a joke, solve a puzzle—and then track the parts of the brain to which blood flows. What results is a picture of the brain spotted with colored blotches in the regions that were active—a satellite weather map showing where the brain clouds were gathering.

But can that be the whole story? There's a deeper answer to be had at infinitecat.com, where users post pictures of their cats gazing at pictures of other cats already posted on the Infinite Cat site. You see an infinite regress: pictures of cats looking at pictures of cats looking at pictures of cats.

Remind you of anything? Those cats are like so many bloggers sitting at home staring into their computer screens and watching other bloggers blog other bloggers. Cats, who live indoors and love to prowl, are the soul of the blogosphere. Dogs would never blog.