Brandeis University, Philosophy Department
Fall 2003
Brandeis University Web Stite

Philosophy 1A

Introduction to Philosophy

Professor Andreas Teuber
Prof. Teuber

Between a Rock and a Hard Place

Can You Never Really Know Anything?

Peter Unger
Ignorance: A Case for Scepticism
Oxford University Press London, 1975.

We begin by arbitrarily choosing something concerning the external world which might conceivably, we suppose, be known, in one way or another, e.g., that there are rocks or, as we will understand it, that there is at least one rock.

Now, first, if someone, anyone knows that there are rocks, then the person can know the following quite exotic thing: There is no evil scientist deceiving him into falsely believing that there are rocks. This scientist uses electrodes to induce experiences and thus carries out his deceptions, conceming the existence of rocks or anything else. He first drills holes painlessly in the variously colored skulls, or shells, of his subjects and then implants his electrodes into the appropriate parts of their brains, or protoplasm, or systems. He sends patterns of electrical impulses into them through the electrodes, which are themselves connected by wires to a laboratory console on which he plays, punching various keys and buttons in accordance with his ideas of how the whole thing works and according to his deceptive designs. The scientist's delight is intense, and it is caused not so much by his exercising his scientific and intellectual gifts as by the thought that he is deceiving various subjects about all sorts of things. Part of that delight is caused, on this supposition, by his thought that he is deceiving a certain person, perhaps yourself, into falsely believing that there are rocks. He is, then, an evil scientist, and he lives in a world which is entirely bereft of rocks.

Now, as we have agreed, (1) if you know that there are rocks, then you can know that there is no such scientist doing this to you, [i.e., deceiving you to falsely believe that there are rocks. But (2) no one can ever know that this exotic situation does not obtain; no one can ever know that there is no evil scientist who is, by means of electrodes, deceiving him into falsely believing there to be rocks. That is our second premise, and it is also very difficult to deny. So, thirdly, as a consequence of these two premises, we have our skeptical conclusion: (3) You never know that there are rocks. But, of course, we have chosen our person, and the matter of there being rocks, quite arbitrarily, and this argument, it surely seems, may be generalized to cover any external matter at all. From this, we may conclude, finally, that (4) nobody ever knows anything about the extemal world.

An attempt to reverse our argument might proceed like this: (1) According to your argument, nobody ever knows that there are rocks. (2) But I do know that there are rocks. This is something concerning the extemal world, and I do know it. Hence, (3) somebody does know something about the external world . . . And so, while I might not have known before that there is no such scientist, at least (4) I now do know that there is no evil scientist who is deceiving me into falsely believing that there are rocks. So far has the skeptical argument failed to challenge my knowledge successfully that it seems actually to have occasioned an increase in what I know about things.

While the robust character of this reply has a definite appeal, it also seems quite daring. Indeed, the more one thinks about it, the more it seems to be somewhat foolhardy and even dogmatic. One cannot help but think that for all this person really can know, he might have all his experience artificially induced by electrodes, these being operated by a terribly evil scientist who, having an idea of what his "protege" is saying to himself, chuckles accordingly.

Suppose you were this person. Now, suppose [too] that the electrodes are removed and that your experiences are now brought about through your perception of actual surroundings, and you are, so to speak, forced to encounter your deceptive tormentor. Wouldn't you be made to feel quite foolish, even embarrassed, by your claims to know? Indeed, you would seem to be exposed quite clearly as having been, not only wrong, but rather irrational and even dogmatic.

It seems much better, perhaps perfectly all right, if you are instead only confident that there is no such scientist. It seems perfectly all right for you to believe there to be no evil scientist doing this. If you say, not only that you believe it, but that you have some reason to believe this thing, what you say may seem somewhat suspect, at least on reasoned reflection, but it doesn't have any obvious tint of dogmatism or irrationality to it . . . Largely because it is so exotic and bizarre, the case of a deceiving scientist lets one feel acutely the apparent irrationality in thinking oneself to know. But the exotic cases have no monopoly on generating feelings of irrationality.

[For example,] you may think you know that a certain city is the capitol of a certain state, and you may feel quite content in this thought while watching another looking the matter up in the library. You will feel quite foolish, however, if the person announces the result to be another city, and if subsequent experience seems to show that announcement to be right. This will occur, I suggest, even if you are just an anonymous, disinterested bystander who happens to hear the question posed and the answer later announced.

This is true even if the reference was a newspaper, The Times, and the capitol was changed only yesterday. But these feelings will be very much less apparent, or will not occur at all, if you only feel very confident, at the outset, that the city is thus-and-such, which later is not announced. You might of course feel that you shouldn't be quite so confident of such things, or that you should watch out in the future. But you probably wouldn't feel, I suggest, that you were irrational to be confident of that thing at that time. Much less would you feel that you were dogmatic in so being.

It is hard for us to think that there is any important similarity between such common cases as these and the case of someone thinking himself to know that there are rocks. Exotic contrast cases, like the case of the evil scientist, help one to appreciate that these cases are really essentially the same. By means of contrast cases, we encourage thinking of all sorts of new sequences of experience, sequences which people would never begin to imagine in the normal course of affairs. How would you react to such developments as these, no matter how exotic or unlikely? It appears that the proper reaction is to feel as irrational about claiming knowledge of rocks [in the case of the evil scientist] as you felt before, where, e.g., one was apparentry caught in thought by the library reference to a State's capitol. Who would have thought so, before thinking of contrast cases? These cases help you see, I suggest, that in either case, no matter whether you are in fact right in the matter or whether wrong, thinking that you know manifests an attitude of dogmatism. Bizarre experiential sequences help show that there is no essential difference between any two external matters; the apparently most certain ones, like that of rocks [in the case of the evil scientist], and the ones where thinking about knowing appears, even without the most exotic skeptical aids [in the case of being wrong about a State's capitol].


[PHIL 1A] [Syllabus] [Handouts] [Home] [Bio] [CV] [PHIL DEPT.] [E-MAIL]

Send comments to: Andreas Teuberr
Last Modified: 03/26/02
Instructor's Toolkit
Copyright © The President and Fellows of Harvard College