Walking along a rocky beach, you notice that rocks and pebbles of different sizes have been arranged according to size in neat bands by the mindless interaction of waves and shore, the ordering effect of differential stability of material arrangements that is no more, and no less, than natural selection itself. A little farther down, you crouch by a tide pool and find, of all things, an old-fashioned pocket watch lying among the seaweed and anemones. The seaweed and anemones are easy enough to understand – natural selection along with the effects of heritable variation, and a lot of time, suffice to account for the lifeforms. The watch is a bit more of a puzzle. Perhaps William Paley has been by, seeding the beach with watches, trying to get us to think, proving the existence of God. That would certainly account for it.

Of course, it's not enough to merely propose a hypothesis that would account for the data, if it were true. Paley has been dead for almost two hundred years, and although it is possible that his spirit roams the earth dispensing watches, that's probably not where the watch came from, however well that would explain its presence.

Paley asked us to consider whether, finding a watch on the beach, we would note its organized complexity and fitness to its task. From this observation, would we infer that it was the result of random physical processes, or would we infer that it was the product of intelligent design?