The Puddle's Pothole is an illustration of the failings of the Fine-Tuning Argument. The counter-argument was told by Douglas Adams to Richard Dawkins, and reported by Dawkins at Adams's funeral on 17 September 2001. The anecdote describes a puddle of water that "wak[es] up one morning and think[s], 'This is an interesting world I find myself in – an interesting hole I find myself in – fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!'"
In the illustration, the puddle assumes that the pothole it resides in was designed specifically for it based on the fact that the dimensions of the pothole match exactly the dimensions of the puddle. This is meant to highlight the flaws in the concept that the universe (specifically the Earth) was specifically designed for our kind of life (human life in particular) based on the fact that the conditions of the universe match exactly the conditions necessary for our kind of life.
Adams's analogy demonstrates that the Fine-Tuning Argument is the result of an interverted conception of the universe. In the same way that, in actuality, it is the molecules of water in the puddle that conform to the dimensions of the pothole, it is our kind of life that conforms to the parameters of the universe.
- "Lament for Douglas," by Richard Dawkins (09/17/01)