> Reasonable people can disagree what counts as a positive vs negative externality. Eg if you like to be warm, perhaps you see global warming as positive extern

> Reasonable people can disagree what counts as a positive vs negative externality. Eg if you like to be warm, perhaps you see global warming as positive externality. I know this was just an example (and you said you weren't entirely happy with it), but the thing about externalities is that yeah someone may like it warm, but just because the damage doesn't happen where you are, doesn't mean it does not happen. E.g. I could totally argue that I like draining that old oil from my car into the river next door since the river flows by and will carry the dirt away from my house. I externalize the pollution I'd have to deal with to the environment where other people live. Just because that cost is not affecting me in regards to that individual act, does not mean I didn't produce it. Or to stay with the climate example: Yeah someone might like it warmer, but do they also like rising sea levels, more extreme wheather events, draught, higher food prices, climate migration, the cultural changes it brings and/or the violence coming from trying to prevent it? And what when the temperature is reached that they no longer like? Climate systems have multiple decades of lag, so when they decide to stop the tanker moves on, and on, and on. Externalities are called that because they have to be paid by someone or something eventually. And not pricing them in is how you get neighbours who start to throw their dirt onto your lawn.