The pitch is right there in the subtitle, the octopus, the sea, and the deep origins of consciousness, and I went in a little worried it would be one of those “animals are secretly smart” books that oversells cute anecdotes and calls it a thesis. It isn’t that. Godfrey-Smith is a philosopher of science who’s also a scuba diver, and the book earns its claims the slow way, walking backward from octopus behavior into the actual evolutionary split, our most recent common ancestor with cephalopods is so far back and so simple that any mental complexity we share isn’t inherited, it evolved twice, independently, which is a genuinely strange thing to sit with.

The line that’s stuck with me hardest, meeting an octopus is probably the closest thing we’ll get to meeting an intelligent alien without leaving the planet, comes up in some form in review after review and I understand why, it’s the whole book in one sentence and it’s not hype, the chapters on distributed neurons, most of an octopus’s neurons live in its arms, not its central brain, back it up with real detail. I also liked that he stays disciplined about not speculating past the evidence on the harder philosophical questions, he sets up big questions about subjective experience and then mostly declines to answer them with certainty he doesn’t have, which some readers found frustrating and I found honest.

If I have a complaint it’s a small one, I wanted one more chapter pushing further into the speculative territory he keeps circling and declining to enter, given how strong his instincts clearly are elsewhere in the book.

Five stars. I reread the octopus-arm chapter twice before moving on, which I basically never do with nonfiction.