The Anthropic Principle: high minds and High Table

The Anthropic Principle is a way for physics to deal with awkward "why?" questions. It answers "Why is the world like this?" with "Because if it weren't, you wouldn't be here to ask the question". We are here, in other words, because we're here because we're here.

J.R. Lucas gives an excellent example of the Anthropic Principle in his classic "high-don" and "low-don" arguments for the world having at least three dimensions. Why are there not just two dimensions? The high don answers that in two dimensions we wouldn't be able to think intelligently; the low don answers that in two dimensions we wouldn't be able to eat without stopping. (More respectably: in two dimensions there is little scope for non-intersecting neural connections; and a creature with a gut would be split by the gut into two creatures).