“It is certainly conceivable, as at least one well-known physicist has speculated (to hoots from most of his colleagues), that the human brain takes advantage of quantum mechanical effects. Yet there is no evidence whatsoever that this is the case. Certainly, the physics of a neuron depends on quantum mechanics, just as the physics of a transistor does, but there is no evidence that neural processing takes place at the quantum mechanical level as opposed to the classical level; that is, there is no evidence that quantum mechanics is necessary to explain human thought. As far as we know, all the relevant computational properties of a neuron can be simulated on a conventional computer. If this is indeed the case, then it is also possible to simulate a network of tens of billions of such neurons, which means, in turn, that the brain can be simulated on a universal machine. Even if it turns out that the brain takes advantage of quantum computation, we will probably learn how to build devices that take advantage of the same effects—in which case it will still be possible to simulate the human brain with a machine.”