But, someone will say, the improbable happens all the time. It is not at all improbable that something improbable should happen. Consider an example. You play a rubber of bridge involving, say, five deals. The probability that the cards should fall just as they do for those five deals is tiny—something like one out of ten to the 140th power. Still, they did. Right. It happened. The improbable does indeed happen. In any fair lottery, each ticket is unlikely to win; but it is certain that one of them will win, and so it is certain that something improbable will happen. But how is this relevant in the present context? In a fit of unbridled optimism, I claim that I will win the Nobel Prize in chemistry. You quite sensibly point out that this is extremely unlikely, given that I have never studied chemistry and know nothing about the subject. Could I defend my belief by pointing out that the improbable regularly happens? Of course not: you cannot sensibly hold a belief that is improbable with respect to all of your evidence.

NAGEL GOES ON: he thinks it is especially improbable that consciousness and reason should come to be if materialist naturalism is true. “Consciousness is the most conspicuous obstacle to a comprehensive naturalism that relies only on the resources of physical science.” Why so? Nagel’s point seems to be that the physical sciences—physics, chemistry, biology, neurology—cannot explain or account for the fact that we human beings and presumably some other animals are conscious. Physical science can explain the tides, and why birds have hollow bones, and why the sky is blue; but it cannot explain consciousness. Physical science can perhaps demonstrate correlations between physical conditions of one sort or another and conscious states of one sort or another; but of course this is not to explain consciousness. Correlation is not explanation. As Nagel puts it, “The appearance of animal consciousness is evidently the result of biological evolution, but this well-supported empirical fact is not yet an explanation—it does not provide understanding, or enable us to see why the result was to be expected or how it came about.”

Nagel next turns his attention to belief and cognition: “the problem that I want to take up now concerns mental functions such as thought, reasoning, and evaluation that are limited to humans, though their beginnings may be found in a few other species.” We human beings and perhaps some other animals are not merely conscious, we also hold beliefs, many of which are in fact true. It is one thing to feel pain; it is quite another to believe, say, that pain can be a useful signal of dysfunction. According to Nagel, materialist naturalism has great difficulty with consciousness, but it has even greater difficulty with cognition. He thinks it monumentally unlikely that unguided natural selection should have “generated creatures with the capacity to discover by reason the truth about a reality that extends vastly beyond the initial appearances.” He is thinking in particular of science itself.

Natural selection is interested in behavior, not in the truth of belief, except as that latter is related to behavior. So concede for the moment that natural selection might perhaps be expected to produce creatures with cognitive faculties that are reliable when it comes to beliefs about the physical environment: beliefs, for example, about the presence of predators, or food, or potential mates. But what about beliefs that go far beyond anything with survival value? What about physics, or neurology, or molecular biology, or evolutionary theory? What is the probability, given materialist naturalism, that our cognitive faculties should be reliable in such areas? It is very small indeed. It follows—in a wonderful irony—that a materialistic naturalist should be skeptical about science, or at any rate about those parts of it far removed from everyday life.