For a more concrete widget example: self-driving cars will have negative externalities on professional drivers. I'm not sure what definition of externalities in

For a more concrete widget example: self-driving cars will have negative externalities on professional drivers. I'm not sure what definition of externalities includes climate change, but not job losses. I also think it's a bit simplistic: what if we find that the carbon energy sector is not capturing all the value of what it provides and has positive externalities that outweigh the negatives at current levels? What do you do about systems with non-linear effects like the climate? I think we shouldn't try and seek a general operating principle from a known hard problem that we are failing to address and is pretty different from others we face. We should have a carbon tax, because it is a useful tool in fighting this battle, not because it is the right tool for every issue.