Economists vs. environmentalists

 Economics and environmentalism are belief systems that shape their adherent's way of thinking about the world.

                                                --Robert H. Nelson (link) 

When I earned my PhD, I started doing God's work (link to funny essay, "The Market as God") at the Justice Department, challenging anticompetitive mergers and putting price-fixers in prison.  My housemate was trying to do the same at the Environmental Protection Agency, using marginal analysis to design incentives to get polluters to face the consequences of their behavior.  If polluters produce up to the point where

    MR=MC

an output tax equal to the harm they cause, T=P, would bring pollution down to the point where the benefits of producing more are equal to its costs, including the costs of pollution.

    MR=MC+T.

There is legitimate debate about the magnitude of P but the principle seems obvious.  But not to [some/many?] environmentalists at the EPA.  They worship another God, and view all pollution as heresy.

In 2009, this debate made it up to the Supreme Court, where the economists prevailed, 6-3:

...the Supreme Court overturned [Sotomayor's earlier appellate decision that straightforward benefit-cost analysis was illegal] in a 6-3 ruling...

For the time being, benefit-cost analysis is OK.