Fighting words from Arnold Kling:

Which do you think takes a bigger toll on the environment, owning a dog, or owning an SUV? My bet would be on the dog. I'm thinking of all of the resources that go into dog food.

Rebuttals in the comments here and here:

My dog presumably values his life a lot more than an SUV values its existence.

My dog creates plenty of negative externalities (barking, excreting, etc.) but also many positive externalities. Walking a cute dog in a big city I am constantly stopped by people who want to pet him and walk away smiling. He facilitates interaction between strangers, which is important for neighborliness and very rare in crowded cities. In contrast, I rarely see people who stop and touch an SUV, smile at the owner and walk away happier.

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