Greg Mankiw welcomes Gary Johnson to the Pigou Club. Let's hope Johnson qualifies for the upcoming debates!
Here he is showing more sense than I've become accustomed to from presidential candidates of late:
"I’m open also to the notion of a carbon tax. That it does have an impact, that it ends up being revenue-neutral. I’m not looking at this as a revenue generator, as much as there are costs associated with, there are health and safety issues with carbon."