Steven Pinker -- How the Mind Works - Hampshire High Italian ...

Revenge of the Nerds 173At this point the critic can say that the criterion—seeing versus notseeing—is set a posteriori, after we know what animals can do, so theprobability estimates are meaningless. They are like the infinitesimalprobability that I would have been dealt whatever poker hand I happenedto have been dealt. Most hunks of matter cannot see, but thenmost hunks of matter cannot flern either, where I hereby define flern asthe ability to have the exact size and shape and composition of the rock Ijust picked up.Recently I visited an exhibition on spiders at the Smithsonian. As Imarveled at the Swiss-watch precision of the joints, the sewing-machinemotions by which it drew silk from its spinnerets, the beauty and cunningof the web, I thought to myself, "How could anyone see this and notbelieve in natural selection!" At that moment a woman standing next tome exclaimed, "How could anyone see this and not believe in God!" Weagreed a priori on the facts that need to be explained, though we disagreedabout how to explain them. Well before Darwin, theologians suchas William Paley pointed to the engineering marvels of nature as proof ofthe existence of God. Darwin did not invent the facts to be explained,only the explanation.But what, exactly, are we all so impressed by? Everyone might agreethat the Orion constellation looks like a big guy with a belt, but thatdoes not mean we need a special explanation of why stars align themselvesinto guys with belts. But the intuition that eyes and spiders show"design" and that rocks and Orion don't can be unpacked into explicitcriteria. There has to be a heterogeneous structure: the parts or aspectsof an object are unpredictably different from one another. And therehas to be a unity of function: the different parts are organized to causethe system to achieve some special effect—special because it is improbablefor objects lacking that structure, and special because it benefitssomeone or something. If you can't state the function more economicallythan you can describe the structure, you don't have design. A lensis different from a diaphragm, which in turn is different from a photopigment,and no unguided physical process would deposit the threein the same object, let alone align them perfectly. But they do havesomething in common—all are needed for high-fidelity image formation—andthat makes sense of why they are found together in aneye. For the flerning rock, in contrast, describing the structure andstating the function are one and the same. The notion of function addsnothing.