The idea that collective intelligence is its own independent entity, that we can contribute to, from the bottom up. You more commonly hear about how collective centralized planning fails, and less about how trade and specialization succeed. Liked that.
There's a lot of talk about how the infrastructure for sharing ideas has improved dramatically over the years — i.e. the internet — and how that allows for a new scale of prosperity, since prosperity is based on the sharing of good ideas. However, Ridley doesn't really touch on how that same scale might make us vulnerable. Where a bad idea of a previous generation might've ruined a place, caused a localized issue; now we have the potential for global ruin.
That prosperity now is worth something that can be discounted against prosperity in the future. That's vital for weighing big future risks. That oil now prevents suffering and improves people's lives. These things do need to be accounted for, and they often aren't. And the inefficiencies of the proposed alternatives, being glossed over for fashionable reasons, that also needs to be addressed. But at the same time, you don't hear Ridley really attack or dismantle the terms of the claimed risks (e.g. Climate Change) so much as rail on the currently offered solutions. He simply holds climate change, as an ambiguous boogieman, up against things like acid rain, which are less worried about today. But this doesn't address the more concrete claims of, say, rising sea levels.
Not a compressive summary or review. Neither an endorsement or criticism. Just some lingering thoughts.