Nagel’s central idea is that there are things that science, as it is presently conceived, cannot possibly explain. The current conception is that, given a purely physical beginning, everything else – chemistry, biology, life, mind, consciousness, intelligence, values, understandings, even science – follows on by natural processes. Particles beget atoms beget molecules beget enzymes beget proteins beget life begets Homo sapiens who begets the Royal Society and the rules of tennis. We do not understand every step in this process, naturally, but we can be reasonably confident of its overall shape and confident, too, that any remaining gaps that can be closed will be closed only by more understanding of the same broad kind that we already have.
Nagel wholly rejects this picture. He denies that our consciousness can be explained in terms of our animal make-up; he thinks it very implausible to suppose that life can be explained as emerging from physical and chemical processes; he doubts that a process of random genetic mutation coupled with natural selection can explain the abundance and complexity of life. He proposes, instead, that there should be an alternative that makes ‘mind, meaning and value as fundamental as matter and space-time in an account of what there is.’