Inferring and Explaining

14 InferrIng and exPlaInIng Dr. Malgenius tricked you about almost every detail about yourself in the little story above. I shall consider myself as not having hands or eyes, or fesh, or blood or senses, but falsely believing that I have all of these things. 6 Could the trick be so perfect that he fools you into believing that you exist, evenwhen you don’t?We have already seen that he can fool you about how you exist—you’re just a brain in a vat afer all. But could he cause you to be mistaken about the very fact of your existence? Descartes thought not. But I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no hands, no minds, no bodies. Does it not follow that I too do not exist? No: if I convincedmyself of something then I cer- tainly existed. But there is a deceiver of supreme power and cunningwho is deliberately and constantly deceiv- ing me. In that case I too undoubtedly exist, if he is deceivingme; and let himdeceiveme asmuch as he can, he will never bring it about that I amnothing so long as I think that I amsomething. So afer considering every- thing very thoroughly, I must fnally conclude that the proposition, I am, I exist, is necessarily truewhenever it is put forward by me or conceived in my mind. 7 Te confdence-undermining possibilities discussed above, I hope, were somewhat com- pelling. But so is the following bit of reasoning. If I am mistaken about what the gas gauge is saying, there must be a “me” who is mistaken. If I am having a dream about all this stuf, there must be a “me” who is doing the dreaming. If I am a brain in a vat being tricked by a perfect computer illusion, there must be a “me” who is fooled by this illusion. In a diferent work on these same topics, Descartes expressed this insight in the famous Latin phrase Cogito ergo sum —I think, therefore I am. Tere must be a “me”who is doing the thinking any time I engage in skeptical thinking, and so it appears that one thing remains immune from the confdence- undermining possibilities of skeptics. Skeptics might respond to this last consider- ation in a couple of ways. Te dyed-in-the-wool skeptic might remind us that Dr. Malgenius was able to trick us about things such as 2 + 3 = 5 and all bachelors being unmarried. Maybe he is causing us to think that it is self-evident that there must be a “me” in order for Malgenius to fool us when in fact this thought is utterly fal- lacious. I, personally, am willing to concede Descartes’s point that complete skepticism is ruled out by the Cogito argument. But we must remember that we have gained damn little, a technical victory over the skeptic, at best. If all that I can claim to know is that I exist, then all mathematics, science, and the everyday world are closed of. But these are precisely the areas where questions about what we know are the most interesting and the most important. The Quest for Certainty It is time to take stock of the arguments so far. Have the skeptics really forced us to abandon most of what we previously thought we knew? If you are like me, you’re not very happy with this conclusion. Unfortunately, logic and good evidence ofen lead us to conclusions that we don’t like but have to accept. Is there any hope for salvaging science and common sense as reli- able sources of knowledge? Maybe, but frst, we have to concede some ground to the skeptic.