In his book “Mind and Cosmos,” Nagel argues that humans should resist assuming that the tools at their disposal are sufficient to understand the universe as a whole. The limits of science should be identified through philosophical inquiry, and this may eventually lead to the discovery of new forms of scientific understanding. Nagel believes there are empirical reasons to be skeptical of reductionism in biology, which is the orthodox view of physico-chemical reductionism. Doubts about the reductionist account of life go against the dominant scientific consensus. Nagel argues that if contemporary research in molecular biology leaves open the possibility of legitimate doubts about a fully mechanistic account of the origin and evolution of life, then principles of a different kind are also at work in the history of nature, which are in their logical form teleological rather than mechanistic.
Nagel is stimulated by criticisms of the prevailing scientific world picture from the religious perspective of intelligent design. Nagel argues that the empirical arguments offered by defenders of intelligent design against the likelihood that the origin of life and its evolutionary history can be fully explained by physics and chemistry are of great interest in themselves. Nagel believes that the prevailing doctrine that life’s appearance from dead matter and its evolution through accidental mutation and natural selection involved nothing but the operation of physical law cannot be regarded as unassailable. While Nagel does not regard the design alternative as a real option, he argues that it is a real question whether the appearance of life from dead matter and its evolution to its present forms is a result of physical laws alone.
In Nagel’s article “What is it like to be a bat?”, he argues that there are certain subjective experiences that cannot be fully captured by objective scientific analysis. Specifically, he points out that the subjective experience of echolocation, which is used by bats to navigate, cannot be fully understood through the objective analysis of the physical properties of echolocation.
Nagel believes that subjective experience is a fundamental aspect of consciousness and that it cannot be reduced to objective physical processes. He argues that even if we knew everything about the physical processes involved in echolocation, we still wouldn’t know what it’s like to actually experience it as a bat does.
Nagel’s point is that subjective experiences are just that: subjective. They cannot be fully understood or captured by objective analysis. While science can tell us a lot about the physical processes that underlie subjective experiences, it cannot fully capture what it is like to actually experience them.
Throughout the book, Nagel explores the shortcomings of both theism and naturalistic reductionism in providing a comprehensive understanding of the natural order. Nagel argues that theism, which posits a transcendent mind to explain the world, fails to offer a comprehensive account of the natural order. While theism admits the reality of more than naturalistic reductionism, it pushes the quest for intelligibility outside the world and leaves out the kind of intelligibility that would explain how beings like us fit into the world. Naturalistic reductionism, on the other hand, tries to make the natural order internally intelligible, but its explanations are not reassuring enough. Nagel asserts that evolutionary naturalism provides an account of our capacities that undermines their reliability, and in doing so, undermines itself. He suggests that there may be a completely different type of systematic account of nature that can accommodate a richer set of materials than the austere elements of mathematical physics, and provide a unifying conception of the natural order. Nagel argues that the ambition of encompassing ourselves in an understanding that arises from but then transcends our own point of view is just as important as the difference between theism and naturalistic reductionism.
Nagel is exploring alternatives to the materialist version of evolutionary theory and the speculative chemical account of the origin of life. He asks what alternatives open up if psychophysical reductionism is rejected. For theists, it remains an option that God created conscious beings either by assembling them out of elements with protopsychic properties or by creating a universe with the appropriate highly specific initial conditions to give rise to conscious beings through chemical and then biological evolution, entirely by non-teleological laws of interaction among the elements.
For a secular theory, there seem to be only two alternatives: either the historical development of conscious life depends entirely on efficient causation, operating in its later stages through the mechanisms of biological evolution, or there are natural teleological laws governing the development of organization over time, in addition to laws of the familiar kind governing the behavior of the elements. Nagel acknowledges that the idea of teleological laws is coherent and should not be ruled out a priori.
Nagel also discusses the problem of explaining our ability to arrive at objective factual or practical truth that goes beyond what perception, appetite, and emotion tell us. This explanation requires an understanding of our ability to acquire and use language, which presents normatively governed faculties. Nagel explores the likelihood that the process of 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 concludes that any evolutionary account of the place of reason presupposes reason’s validity and cannot confirm it without circularity.
Nagel argues that a theory of everything must explain not only the emergence of life from a lifeless universe and its development by evolution to greater and greater functional complexity but also the consciousness of some organisms and its central role in their lives. Furthermore, it must explain the development of consciousness into an instrument of transcendence that can grasp objective truths beyond what perception, appetite, and emotion tell us.
On page 97, Nagel argues that the natural order must explain the possibility of rational beings, and the world must have properties that make their appearance not a complete accident, which requires both a constitutive and historical explanation. The understanding of biological organisms and their evolutionary history would have to expand to accommodate this additional explanatory burden, as he argues that it must expand beyond materialism to explain consciousness.
On page 98, Nagel rejects the metaphor of the mind as a computer built out of a huge number of transistor-like homunculi, as it omits the understanding of the content and grounds of thought and action essential to reason. He suggests that a holistic or emergent answer to the constitutive question comes to seem increasingly more likely than a reductive one as we move up from physical organisms to consciousness and reason, meaning that reason is an irreducible faculty of the fully formed conscious mind that exists in higher animals and cannot be analyzed into the activity of the mind’s protomental parts.
On page 116, Nagel discusses the implications for the natural order of different conceptions of value. He agrees with Sharon Street’s position that moral realism is incompatible with a Darwinian account of the evolutionary influence on our faculties of moral and evaluative judgment, and follows the same inference in the opposite direction: since moral realism is true, a Darwinian account of the motives underlying moral judgment must be false, in spite of the scientific consensus in its favor.
On page 139, Nagel concludes that the truth about the natural order may be beyond our reach due to our intrinsic cognitive limitations, but it makes sense to continue seeking a systematic understanding of how we and other living things fit into the world. He argues against the prevailing form of naturalism, a reductive materialism that purports to capture life and mind through its neo-Darwinian extension, and finds it antecedently unbelievable. He believes that the present right-thinking consensus will come to seem laughable in a generation or two, but the human will to believe is inexhaustible.