Wittgenstein had a hard time getting this point across. The simple truth at the heart of his argument was unacceptable to thinkers convinced that philosophy could address many problems plaguing humanity. To take his point would put a lot of professors out of work. Yet he tried desperately to make himself clear, from his earliest words to his last. In the preface to his first book he wrote, "The whole sense of the book might be summed up in the following words: what can be said at all can be said clearly, and what we cannot talk about we must pass over in silence." Indeed, he has often been called a mystic.
In fact, he wanted philosophers to shut up about most of what matters in everyday life: ethics, aesthetics, nature, religion. On such subjects, formal languages like logic and science can only send us off "in pursuit of chimeras." It is because these formal languages follow strict rules and rule out contradictions that they lack common sense and give a misleading view of the world. "It is like a pair of glasses on our nose through which we see whatever we look at," he admonished his colleagues. "It never occurs to us to take them off." As for his attacks on philosophy, he said, "What we are destroying is nothing but houses of cards."
Poor Popper didn’t have a clue. He was a paragon of pure reason armed only with logic, confronting the mind of a mystic uttering paradoxes and waving a poker in the air. Popper was best known for his book The Open Society and Its Enemies, which attacked Communism and challenged Marxist theory as pseudoscience. Wittgenstein waved this off as the concern of sociology. He had more universal fish to fry. "Philosophy," he said, "is a battle against the bewitchment of our intelligence by means of language."
Although Wittgenstein, who died in 1951 at age 62, did not live to see the most striking example of this bewitchment—the pursuit of artificial intelligence in computers—his ghost sat next to me at a seminar on this subject at the Smithsonian Castle in the 1980s. Bill Woods, a scientist who had struggled to make computers understand ordinary language, offered a confession. "We assumed," he said, "we could start with simple children’s stories and work our way up to complex fields like physics and astronomy. It turned out that understanding physics and astronomy is extremely simple compared to the problem of understanding children’s stories." Bewitchment indeed, muttered Wittgenstein’s ghost.
The ghost turned up again a few years later when I was talking to another artificial intelligence pioneer, John McCarthy, at Stanford University. McCarthy was explaining his efforts to impart reason to computers. "I estimate there are only about 12 or 13 rules that are needed for the logic of common sense," he said. "I’ve figured out 5 of them, and I’m sure we’ll understand the rest in a few years. Then we can program any computer with common sense." That achievement, as it turned out, has proved elusive.
Our scientists and philosophers are still misleading us in their pursuit of chimeras. Lately, the talk of cloning people has got Wittgenstein’s ghost reaching for his poker again. We are dealing with imponderables once more, and talking as if we knew what we’re talking about when we don’t.
The actual poker Wittgenstein waved at Popper back in 1946 mysteriously disappeared after the incident. But Wittgenstein’s ghost, ever skeptical, still brandishes it.