There is an old philosophical argument based upon the assumption that a good design presupposes an intelligent agency. If we encounter efficient machines, we must assume an intelligent planner. In the nineteenth century, biologists discounted this assumption. Suppose, they argued, structural changes do occur in living organisms by chance only. Nevertheless, the changes which register will be mostly in a given direction, since those less efficiently designed will not survive. In this way, highly efficient and extraordinarily complicated designs will “evolve” without any intelligent planning simply because (1) the capacity to survive is a “scoring” mechanism and (2) in a long interval of time there will be many generations.