Scott Pruitt, Donald Trump’s nominee to lead the Environmental Protection Agency, has raised more hackles among progressive Democrats than any other Trump cabinet nominee. Typical of the ferocious opposition to his candidacy is the screed prepared by the Sierra Club that deems him a mortal threat to the safety of the planet because, as Attorney General in Oklahoma, he has “spent his time in office working to allow big polluters to do whatever they want, rather than protecting the health, clean air and water of his constituents.” Democrats like Senator Brian Schatz of Hawaii have insisted that his nomination is “a four-alarm fire” because Pruitt is a pawn of fossil fuel companies whose cardinal sin is denying the conclusion of “climate scientists” that human emission of carbon dioxide is creating a global warming crisis.

The defenders of Pruitt have been equally vocal. President Trump, no man to mince words, has railed against the EPA for spending “taxpayer dollars on an out-of-control anti-energy agenda that has destroyed millions of jobs, while also undermining our incredible farmers and many other businesses and industries at every turn.” In his view, Pruitt is needed to restore some sense of balance to the entire enterprise.

So the big question is who is right and why. In order to cut through the strong rhetoric on both sides, it is important to return to first principles to see how the regulation of pollution and jobs fit together. To start, neither the environmentalists nor Pruitt hold the untenable view that pollution is a good thing. But they profoundly disagree on two key second-order questions—the correct definition of pollution and the right remedial structure to deal with its occurrence.