DOCTOR: Oh, so no wonder you doubted it was red! True enough, your eyes perceived the correct color of the book, but your earlier experience lingered in your mind and made it impossible for you to really believe it was red. So the machine was right!
FRANK: Well, all right, but then why did I doubt that I believed it was true?
DOCTOR: Because you didn’t believe it was true, and unconsciously you were smart enough to realize the fact. Besides, when one starts doubting one’s own sense perceptions, the doubt spreads like an infection to higher and higher levels of abstraction until finally the whole belief system becomes one doubting mass of insecurity. I bet that if you went to the epistemologist’s office now, and if the machine were repaired, and you now claimed that you believe the book is red, the machine would concur.
No, Frank, the machine is—or, rather, was—a good one. The epistemologist learned much from it, but misused it when he applied it to his own brain. He really should have known better than to create such an unstable situation. The combination of his brain and the machine each scrutinizing and influencing the behavior of the other led to serious problems in feedback. Finally the whole system went into a cybernetic wobble. Something was bound to give sooner or later. Fortunately, it was the machine.
FRANK: I see. One last question, though. How could the machine be trustworthy when it claimed to be untrustworthy?
DOCTOR: The machine never claimed to be untrustworthy, it only claimed that the epistemologist would be better off not trusting it. And the machine was right.
Reflections
If Smullyan’s nightmare strikes you as too outlandish to be convincing, consider a more realistic fable—not a true story, but surely possible:
Once upon a time there were two coffee tasters, Mr. Chase and Mr. Sanborn, who worked for Maxwell House. Along with half a dozen other coffee tasters, their job was to ensure that the taste of Maxwell House stayed constant, year after year. One day, about six years after Mr. Chase had come to work for Maxwell House, he cleared his throat and confessed to Mr. Sanborn:
“You know, I hate to admit it, but I’m not enjoying this work any more. When I came to Maxwell House six years ago, I thought Maxwell House coffee was the best-tasting coffee in the world. I was proud to have a share in the responsibility for preserving that flavor over the years. And we’ve done our job well; the coffee tastes today just the way it tasted when I arrived. But, you know, I no longer like it! My tastes have changed. I’ve become a more sophisticated coffee drinker. I no longer like that taste at all.”
Sanborn greeted this revelation with considerable interest. “It’s funny you should mention it,” he replied, “for something rather similar has happened to me. When I arrived here, shortly before you did, I, like you, thought Maxwell House coffee was tops in flavor. And now I, like you, really don’t care for the coffee we’re making. But my tastes haven’t changed; my … tasters have changed. That is, I think something has gone wrong with my taste buds or something—you know, the way your taste buds go off when you take a bite of pancakes and maple syrup and then go back to your orange juice? Maxwell House coffee doesn’t taste to me the way it used to taste; if only it did, I’d still love it, for I still think that taste is the best taste in coffee. Now, I’m not saying we haven’t done our job well. You other guys all agree that the taste is the same, so it must be my problem alone. I guess I’m no longer cut out for this work.”
Chase and Sanborn are alike in one way. Both used to like Maxwell House coffee; now neither one likes it. But they claim to be different in another way: Maxwell House tastes to Chase the way it always did, but not so for Sanborn. The difference seems familiar and striking, yet when they confront each other, they may begin to wonder if the cases are really all that different. “Could it be,” Chase might wonder, “that Mr. Sanborn is really in my predicament and just hasn’t noticed the gradual rise in his standards and sophistication as a coffee taster?” “Could it be,” Sanborn might wonder, “that Mr. Chase is kidding himself when he says the coffee tastes just the same to him as it used to?”
Do you remember your first sip of beer? Terrible! How could anyone like that stuff? But beer, you reflect, is an acquired taste; one gradually trains oneself—or just comes—to enjoy that flavor. What flavor? The flavor of that first sip? No one could like that flavor! Beer tastes different to the experienced beer drinker. Then beer isn’t an acquired taste; one doesn’t learn to like that first taste; one gradually comes to experience a different, and likable, taste. Had the first sip tasted that way, you would have liked beer wholeheartedly from the beginning!
Perhaps, then, there is no separating the taste from the response to the taste, the judgment of good or bad. Then Chase and Sanborn might be just alike, and simply be choosing slightly different ways of expressing themselves. But if they were just alike, then they’d actually both be wrong about something, for they each have sincerely denied that they are like the other. Is it conceivable that each could have inadvertently misdescribed his own case and described the other’s instead? Perhaps Chase is the one whose taste buds have changed, while Sanborn is the sophisticate. Could they be that wrong?
Some philosophers—and other people—have thought that a person simply cannot be wrong about such a matter. Everyone is the final and unimpeachable arbiter of how it is with him; if Chase and Sanborn have spoken sincerely, and have made no unnoticed slips of language, and if both know the meanings of their words, they must have expressed the truth in each case. Can’t we imagine tests that would tend to confirm their different tales? If Sanborn does poorly on discrimination tests he used to pass with flying colors, and if, moreover, we find abnormalities in his taste buds (it’s all that Szechuan food he’s been eating lately, we discover), this will tend to confirm his view of his situation. And if Chase passes all those tests better than he used to, and exhibits increased knowledge of coffee types and a great interest in their relative merits and peculiar characteristics, this will support his view of himself. But if such tests could support Chase’s and Sanborn’s authority, failing them would have to undermine their authority. If Chase passed Sanborn’s tests and Sanborn passed Chase’s, each would have doubt cast on his account—if such tests have any bearing at all on the issue.
Another way of putting the point is that the price you pay for the possibility of confirming your authority is the outside chance of being discredited. “I know what I like,” we are all prepared to insist, “and I know what it’s like to be me!” Probably you do, at least about some matters, but that is something to be checked in performance. Maybe, just maybe, you’ll discover that you really don’t know as much as you thought you did about what it is like to be you.
D.C.D.
26
Douglas R. Hofstadter
A Conversation with Einstein’s Brain
The Tortoise and Achilles bump into each other accidentally at the edge of one of the large octagonal ponds in the Jardin du Luxembourg in Paris, where young lads and lasses often take their small sailboats—and, in this day and age, even motorized and radio-controlled boats. But this is beside the point. It is a pleasant fall day.