the braino cap is placed on a subject's head, the operator of the braino can affect his brain so as to produce any hallucination in the subject that the operator wishes. The braino is a hallucination-producing machine. The hallucinations produced by it may be as complete, systematic, and coherent as the operator of the braino desires to make them." The braino argument was intended to show that, even if it is sometimes possible to tell when we are hallucinating, it is not possible to know that we are not hallucinating. If the braino is operated by an evil being, whom Cornman and Lehrer call Dr. O, then it would be possible for Dr. O to create in me experiences that are identical to the ones I am having now. If that were the case, then the experiences thus created would not constitute knowledge, for the source of those experiences would be the machine and not the world. However, since they are indistinguishable from my current experiences, it follows that my current experiences are also insufficient to generate knowledge. In 1973, in the introduction to his book Thought, Gilbert Harman said, "it might be suggested that you have not the slightest reason to believe that you are in the surroundings you suppose you are in ... various hypotheses could explain how things look and feel. You might be sound asleep and dreaming or a playful brain surgeon might be giving you these experiences by stimulating your cortex in a special way. You might really be stretched out on a table in his laboratory with wires running into your head from a large computer. Perhaps you have always been on that table. Perhaps you are quite a different person from what you seem..." Such scenarios had been used many times in science fiction but in philosophy it is now routine to refer to being like a 'brain in a vat' after Hilary Putnam produced an argument which, ironically, purported to show that "the supposition that we are actually brains in a vat, although it violates no physical law, and is perfectly consistent with everything we have experienced, cannot possibly be true. It cannot possibly be true, because it is, in a certain way, self-refuting." Putnam's argument notwithstanding, the brain in a vat scenario is usually presented as a sceptical argument and in many ways equivalent to Descartes' deceiving God and evil demon.