In his book Seven Clues to the Origin of Life, the Scottishchemist A. G. Cairns-Smith makes an additional point, using theanalogy of an arch. A free-standing arch of rough-hewn stones andno mortar can be a stable structure, but it is irreducibly complex: itcollapses if any one stone is removed. How, then, was it built in thefirst place? One way is to pile a solid heap of stones, then carefullyremove stones one by one. More generally, there are manystructures that are irreducible in the sense that they cannot survivethe subtraction of any part, but which were built with the aid ofscaffolding that was subsequently subtracted and is no longervisible.

The God Delusion On page 130 Monday, November 5, 2012 @ 1:54pm