Octopus intelligence, specifically. And the evolution of intelligent nervous systems in general.

Between these two angles lies the fact that Octopus intelligence developed on such a different path, it surely is much like studying Alien intelligence!

I studied Philosophy of Mind during my bachelor program, and I did find it fascinating. I used to think that I'd never dive into these topics again ― that I could only do it in my university years, when I had the time and capacity that only a university student has for such "dry" topics.

Peter Godfrey-Smith convinced me otherwise.

In this book, he combines three major disciplines very nicely:
 

1. Philosophy of Mind:
   • What is conscious subjective thought?
   • What is intelligence?
   • What is the role of our inner monologue in both subjective experience and intelligence?
2. Marine Biology:
   • How does Octopus intelligence work, when they have half their neurons in their arms?
   • How do they create movie-like coloured displays on their skin, and why, if they don't seem to be able to see in colour?
   • Why do Octopus only live between two and four years, given their high complexity?
3. Theory of Evolution:
   • How did inner nervous activity in organisms evolve in the oceans, hundreds of millions of years ago?
   • Did language evolve from an inner feedback loop for control signals?
   • How often has higher intelligence been created during evolution independently?
   • How crucial is social life for intelligence, seeing the octopus don't seem to have too much of it?

There are stories from diving expeditions to a magical Octopus place off the coast of Australia mixed in between all of these deep pondering, making the book quite captivating.

What is also captivating is that during the research for this book, Godfrey-Smith could follow the latest advancements in Octopus research. For instance, the Octopus genome was sequenced in 2015, which back-dated the evolution of intelligence in Octopus and Cuttlefish (it happened independently even within their evolutionary branch!). Also, theories about the ability of the Octopus skin to produce colours were advanced just a few years ago.

This is science journalism at its finest.