A scattershot discourse that gathers and speculates on the wide range of research and philosophy regarding the nature of biological and psychological time. It is an endlessly complex subject, in the midst of which the author often loses focus, but there are many fascinating tidbits along the muzzy way. The concluding chapters are the best. Putting aside the minutiae and uncertainty that hampered his discussion of the body's innate rhythms, Campbell explicates the various speculations on the co-evolution of self-consciousness and time-consciousness. He melds the ideas of Heidegger, Sartre, Julian Jaynes (The Origin of Consciousness in the Breakdown of the Bicameral Mind), William Gaddis, and others, not so much to formulate an answer as to flame a question. The material leading towards the concluding essays is handled less dexterously, though they are nonetheless interesting. The rhythms of speech, sleep, memory, music are linked to our evolutionary past--even if it is by the baldest speculation. The primary weakness of the presentation is that, as a survey of ideas rather than an argument, it doesn't always cohere. Campbell presents too many facts and not enough implications, and his carefully objective voice seems sterile. More naive enthusiasm, and less piling on of different ideas, would better elucidate these complex issues for the general reader, for whom the book is apparently intended.