Solving the world’s biggest problems—from climate catastrophe and pandemics to wildfires and corporate malfeasance—requires, more than anything else, coming up with new ways to manage the powerful interactions that surround us. For carbon emissions and other environmental damage, this means ensuring that those responsible pay their full costs rather than continuing to pass them along to others, including future generations. In The Spirit of Green, Nobel Prize–winning economist William Nordhaus describes a new way of green thinking that would help us overcome our biggest challenges without sacrificing economic prosperity, in large part by accounting for the spillover costs of economic collisions.