… is from page 26 of Richard Epstein’s insightful 2014 Harvard Journal of Law & Public Policy article, “Modern Environmentalists Overreach: A Plea for Understanding Background Common Law Principles ” (footnote excluded):
Knowing when to quit is as important as knowing when to proceed. Any support for creating a pollution-free river fails if it overlooks the need to set marginal benefit equal to marginal cost. In doing so, advocates of a pollution-free position have gone a bridge too far by inventing problems that need no solution. Now the environmentalists themselves become the social problem.
The marginal cost of activity X in excess by dollar amount Z over the marginal benefit of activity X is exactly as harmful to society – $Z – as is the marginal cost of activity Y in excess by dollar amount Z over the marginal benefit of activity Y. This reality holds if X is an industrial activity aimed at earning profits for factory owners who produce goods that satisfy consumer demands while Y is a political activity aimed at reducing X, no less than if X is a political activity aimed at reducing Y while Y is an industrial activity aimed at earning profits for factory owners who produce goods that satisfy consumer demand.
See Ronald Coase .