SENTIENCE

Exploring the philosophical, scientific, and ethical questions of animal sentience.

Humphrey, a theoretical psychologist known for his work on the evolution of consciousness, poses the provocative thought that there needn’t necessarily be a connection between intelligence and sentience, the quality of being self-aware. He argues that numerous species of mammals and birds pass the test of sentience as readily as humans, and he wonders if consciousness as we regard it is an evolutionary accident confined to Earth. This is as much a philosophical as a scientific study, though he devotes careful attention to matters of biological and psychological development. The subtitle contains the pivotal word invention: why sentience emerged and how. Humphrey distinguishes between the terms sentience and consciousness and contends that while a great many animals may possess “cognitive consciousness,” true sentience depends on “phenomenal consciousness,” a product of natural selection. Humphrey’s arguments are both plausible and lucid, the product of exhaustive research and decades spent weighing the possibilities. No less engaging are his ideas on animals as “natural psychologists.” He does concede, however, that his opinions put him in the minority and that his theory remains open to debate. Humphrey evaluates the objections of colleagues and addresses competing theories, including integrated information theory, panpsychism, and illusionism, none of which fare well under his scrutiny. Whether agreeing with him in full, in part, or not at all, the text is a stimulating exercise in experiment and speculation. As a theorist, his approach offers a distinct “wow” factor. Although his expertise is deeper, as a writer on consciousness, he suffers somewhat when compared to Oliver Sacks or Alan Lightman. As with most intersections of science and philosophy, there is a certain amount of esoterica involved as well as some semantic splitting of hairs. But held against his fascinating premise, these are minor quibbles.

Complex and sometimes counterintuitive concepts rendered with admirable skill.