As a skeptic of economics, who never broached 300-level economics, who did broach 300-level statistics, who did get an engineering degree and who has read at least two dozen pop economics books, I can say with much conviction and little credibility that the greatest difficulty economics faces, in every academic dispute about economics, is externality.

I can use economic theory to argue for the EPA: they preserve the value of an asset against unfair exploitation. I can use it to argue against it: they inhibit the full utilization of resources by the stakeholders of the market. AllnI need to do is define "the market" to include or exclude people who breathe but don't pollute.

The externalities of economics have gotten buried in the past forty years because Saint Milton argued that it was the job of business to exclude any stakeholders that were not direct economic components of the problem; he went as far as saying that businesses were required by their duty to their shareholders to extract as much value from the commons as possible, up to and including legal penalties, because any society that valued its environment (for example) would legislate sufficiently harsh penalties. No harsh penalties? Wrll then people are obviously fine with the Cuyahoga catching fire.

The externalities of the political process weren't his problem, of course. He was an economist.

Freakonomics is, down to the last example, a "gotcha!" approach to redefining externalities. Modern Monetary Theory is a redefinition of externalities. Universal Basic Income? A battle to redefine the externalities. So in the end, every economic battle, when you look at it from a systems point of view, is a battle over where to define the system of economics... Amd every article about "new" economics invariably reveals itself to be striking a blow to include some stakeholder or asset that has previously been judged an externality.