In this volume, Thomson answers two fundamental questions in biology: what are living creatures and how have they come to be?

The author begins with a brief examination of origins. His primary focus is on epoch-making steps of the ‘making of bodies’, the specialization of function, the evolution of male and female multicellular individuals, the invention of haemoglobin and the establishment of internal surfaces.

Thomson then looks at three evolutionary factors: variation, selection and heredity. The author sees the latter not in a fatalistic light, ‘the hand of the past has such a heavy grip’, but in a positive way, ‘the persistence of the stable, the continual emergence of the new’. Despite being in the middle of the Great War as he delivered his Gifford Lectures, Thompson still affirms ‘the moral law is as real and as external to any man or in any single nation. It is the work of the blood and tears of long generations of men.’ Thomson draws on traditions, literature and religions as proofs that ‘nature is crowned in man’.