Earlier this month, David Cameron received two open letters from prominent environmentalists, sending conflicting messages. The first letter, written by Jonathon Porritt and three other former presidents of Friends of the Earth, urged the government to abandon nuclear energy. The second letter, written by George Monbiot and four co-authors, denounced the first one and offered a qualified defence of nuclear energy.

To an outsider, it is not immediately clear why a disagreement over nuclear energy should cause a deep rift when the commonalities clearly outweigh the differences. Both sides represent the same authoritarian, anti-growth, anti-market strand of environmentalism. As Monbiot himself points out: ‘Our underlying aim is the same: we all want to reduce human impacts on the biosphere. We all agree that our consumption of resources must be reduced, as sharply as possible. We all question the model of endless economic growth.’  So what’s the problem?

George Monbiot seems to realise that decarbonising the economy is going to be very, very costly. For somebody who is opposed to economic growth and appalled by the sight of people buying and selling stuff, this is not in itself a problem. But he is pragmatic enough to realise that the public’s appetite for a programme of national impoverishment is limited. So he has concluded that considerations of cost-effectiveness should not be totally ignored, and that idolising any one particular carbon abatement technology, regardless of its outcomes, is counterproductive to the overall aim. By implication, this has restrained his enthusiasm for renewable energy (see here and here), which, as The Economist noted, constitutes ‘one of the costliest ways known to man of getting carbon out of the energy system’.

Inevitably, his position has led to harsh criticism from other environmentalists, who have questioned Monbiot’s motives as well as his arguments. And when Monbiot came out reluctantly supporting nuclear energy as a low-carbon alternative to fossil fuels, the attacks grew angrier. Porritt wrote: ‘Your inability (or unwillingness) to track solar costs has marooned you in a weird contrarian crusade to undermine the solar industry – even as you volunteer your services as a mouthpiece for the nuclear industry’. In short, Monbiot was given a taste of his own medicine. He didn’t like it.

Does this strange War of the Roses undermine Monbiot’s earlier claim that his own side’s arguments were based on science, while the other side was populated by flat-earthers? Not necessarily. This has never been a helpful distinction to make. The point is that everybody, in every political debate, is convinced that their own arguments are purely based on facts and evidence. It is always the other guy who is the ideological zealot, the one who refuses to see the facts even though they stare him in the face.

The relevant distinction is not whether this camp or that camp attracts more pigheaded followers. Rather, it is some institutions that reinforce our proclivity for pigheadedness, while others challenge it. Often the same person who acts pigheadedly in one set of circumstances is quite capable of self-correction in a different set of circumstances. Traditional environmentalist policies, unfortunately, provide the perfect playground to nurture one’s own pigheadedness.

This is one reason why the variant of environmental protection based on property rights and incentives is preferable to the state-driven, authoritarian brand represented by both Monbiot and Porritt. On a personal level, the advocates of the former may be just as pigheaded as the advocates of the latter. But at least, they do not advocate policies which further encourage their own pigheadedness.