The obvious truth is that the moment any matter has passed through the human mind it is finally and for ever spoilt for all purposes of science. It has become a thing incurably mysterious and infinite; this mortal has put on immortality. Even what we call our material desires are spiritual, because they are human. Science can analyse a pork-chop, and say how much of it is phosphorus and how much is protein; but science cannot analyse any man’s wish for a pork-chop, and say how much of it is hunger, how much custom, how much nervous fancy, how much a haunting love of the beautiful. The man’s desire for the pork-chop remains literally as mystical and ethereal as his desire for heaven. All attempts, therefore, at a science of any human things, at a science of history, a science of folk-lore, a science of sociology, are by their nature not merely hopeless, but crazy. You can no more be certain in economic history that a man’s desire for money was merely a desire for money than you can be certain in hagiology that a saint’s desire for God was merely a desire for God. And this kind of vagueness in the primary phenomena of the study is an absolutely final blow to anything in the nature of a science. Men can construct a science with very few instruments, or with very plain instruments; but no one on earth could construct a science with unreliable instruments. A man might work out the whole of mathematics with a handful of pebbles, but not with a handful of clay which was always falling apart into new fragments, and falling together into new combinations. A man might measure heaven and earth with a reed, but not with a growing reed.