Sir – Abraham Kaplan’s Law of the Instrument states: “Give a small boy a hammer, and he will find that everything he encounters needs pounding.”

Sadly, Lawrence Haar (First Person, October 10) appears similarly intent on pounding renewable energy technologies with his free market economic hammer. If only his analysis had the breadth of that of fellow economist Nicholas Stern.

Because, wedded as Dr Haar appears to be to the virtues of the free market, he seems somehow to have overlooked the elephant standing next to him, despite the illumination recently shone upon it by the latest (AR5) report from the Intergovernmental Panel on Climate Change.

As Stern noted: “Climate change is a result of the greatest market failure the world has seen.” The Industrial Revolution and all that followed were made possible by tapping ever-greater quantities of non-renewable energy — a capital asset that has thus far been treated as disposable income.

In parallel, our essential and irreplaceable biosphere has been progressively degraded by this profligacy. Having burned much of the Chippendale to keep warm, we are now left with a limited range of options, all of them costly. Dr Haar would do well to tell us which of them he suggests we use to keep the lights on.

Fred Foxon, Merton, nr Bicester