The fear of religion leads too many scientifically minded atheists to cling to a defensive, world-flattening reductionism. Dawkins, like many of his contemporaries, is hobbled by the assumption that the only alternative to religion is to insist that the ultimate explanation of everything must lie in particle physics, string theory, or whatever purely extensional laws govern the elements of which the material world is composed.

This reductionist dream is nourished by the extraordinary success of the physical sciences in our time, not least in their recent application to the understanding of life through molecular biology. It is natural to try to take any successful intellectual method as far as it will go. Yet the impulse to find an explanation of everything in physics has over the last fifty years gotten out of control. The concepts of physical science provide a very special, and partial, description of the world that experience reveals to us. It is the world with all subjective consciousness, sensory appearances, thought, value, purpose, and will left out. What remains is the mathematically describable order of things and events in space and time.

That conceptual purification launched the extraordinary development of physics and chemistry that has taken place since the seventeenth century. But reductive physicalism turns this description into an exclusive ontology. The reductionist project usually tries to reclaim some of the originally excluded aspects of the world, by analyzing them in physical—that is, behavioral or neurophysiological—terms; but it denies reality to what cannot be so reduced. I believe the project is doomed—that conscious experience, thought, value, and so forth are not illusions, even though they cannot be identified with physical facts.

I also think that there is no reason to undertake the project in the first place. We have more than one form of understanding. Different forms of understanding are needed for different kinds of subject matter. The great achievements of physical science do not make it capable of encompassing everything, from mathematics to ethics to the experiences of a living animal. We have no reason to dismiss moral reasoning, introspection, or conceptual analysis as ways of discovering the truth just because they are not physics.

(Thomas Nagel, “The Fear of Religion,” review of The God Delusion, by Richard Dawkins, The New Republic 235 [23 October 2006]: 25-9, at 28-9)