It's also very, very high-dimensional. Imagine a gigantic space, where similar thoughts could be placed next to one another. Thinking would be moving around this space. Free association would be taking a step or two in a random direction. Comparison would be a vector.

This captures a little of the nature of semantic representations (storage of meanings and concepts). But of course, semantic representations differ hugely from, say, representations of a tennis serve, or the phone number you're repeating under your breath while you key it in...