The American economist Paul Romer has recently written of ‘mathiness’, by analogy with ’truthiness’, a term coined by American talkshow host Stephen Colbert. Truthiness presents narratives which, not actually true, but consistent with the world view of the person who spins the story. Truthiness is exemplified in right-wing fabrications about European health systems – their death panels and forced euthanasia – and in feminist support for alleged rape victims even when their allegations are demonstrably false. Mathiness is a similar use of algebraic symbols and quantitative data to give an appearance of scientific content to ideological preconceptions.

It is  characteristic of science to give  precise meaning to concepts, and the basis of their measurement. Every careful person equipped with a reliable thermometer will make the same reading of temperature. There are alternative scales, Fahrenheit and Celsius, but both record the same thing,. We even coin expressions like ‘It feels cold’ to acknowledge  that our subjective experience of temperature may differ from objective fact. And we go on to find scientific explanations ,like wind chill factor, to explain the relationship between the two.

Economics is genuinely harder. National income is a more complicated concept than temperature, and there are plausible alternative sets of rules for calculating it. However serious minded statisticians have spent many years discussing these issues, and there is  now a United Nations  standardised system of national accounts. Given the same underlying observations, most well-trained officials will come up with very similar answers to the question ‘what is national income?’.

But it is easy to write a mathematical symbol without giving thought to what observable fact in  the real world  corresponds to that symbol, or  whether there is such an observable fact at all,. The measurement of capital has always been controversial, in a way the measurement of national income is not, In large part because Karl Marx chose that term for the title of his book. Half a century ago, the measurement of capital was at the centre of an ideologically driven debate; between the Cambridge University Marxist economist Joan Robinson and numerous acolytes, and a group of American scholars led by MIT professor Robert Solow. A debate which Solow won easily because of the care he took to specify both his  models and the data relevant to them. But recently capital measurement and ideology have again become intertwined, through the public attention given to the work of Thomas Piketty, with serious questions raised about the relationship between his data, his theory, and the political stance which motivates his work.

In discussing ‘mathiness’  Romer makes a distinction between what he calls ‘Feynman integrity’ and ‘Stigler conviction’. For the great American physicist Richard Feynman, science involved ‘a kind of leaning over backwards. For example, if you’re doing an experiment, you should report everything that you think might make it invalid–not only what you think is right about it’ – This is a proper aspiration, though an idealised view of science which few scientists actually practice (and few would win tenure if they did)

      But for George Stigler, a founder of the modern Chicago school of economics’, the successful inventor is a one-sided man. He is utterly persuaded of the significance and correctness of his ideas and he subordinates all other truths because they seem to him less important than the general acceptance of his truth.’

The distinction is that made by Tolstoy and Isaiah Berlin, between foxes who know many little things  and hedgehogs who know one big thing. The strange thing about economics is that because practical economics spans both science and politics both characteristics – careful analysis and effective polemic – are required. The geniuses of the subject  – like Adam Smith and J M Keynes – combined both. The practitioners of mathiness lack skill in either.