“To the outside observer, the English monetary system lacked all logic. To the English themselves, however, it was all of a piece with their weights and measures, which were constructed by division rather than addition, and which therefore presented strange angularities of arithmetic: eight pints to the gallon, fourteen pounds to the stone, eight stone to the hundredweight, twelve inches to the foot, three feet to the yard and 1,760 yards to the mile, amazingly – not to speak of rods and perches, gills and tuns. Weights and measures mediate our day-to-day transactions; hence they are imprinted with our sense of membership. They are symbols of the social order and distillations of our daily habits.

The old English measures once had their equivalents on the continent. But, the French believed, they were symbols of a hierarchical, backward-looking society, a society that paid more respect to custom and precedent than to progress and the future. They were muddled, improvised and full of compromises, in just the way that human life is full of compromises when insufficiently controlled. What was needed, the revolutionaries thought, was a system of measures expressive of the new social order, based on Reason, progress, discipline and the future. Since the decimal system is the basis of arithmetic, and since mathematics is the symbol of Reason and its cold imperatives, the decimal system must be imposed by force, in order to shake people free of their old attachments.

The distinction between the imperial and the metric systems corresponds to the distinction between the reasonable and the rational, between solutions achieved through custom and compromise and those imposed by a plan. Muddled though imperial measures may appear to those obsessed by mathematics, they are - unlike the metric system - self-evidently the product of life. In the ordinary, cheerful and yielding transactions between people, measurement proceeds by dividing and multiplying, not by adding. The French revolutionaries believed that by changing weights and measures, calendars and festivals, street-names and landmarks, they could more effectively undermine the old and local attachments of the French people, so as to conscript them behind their international purpose. The survival of the old weights and measures in England testifies to the underlying principle of English society - the principle that society should be governed not from above but from within; by custom, tradition and compromise, and by a habit of reasonableness of which the single most important enemy is Reason. English measures were designed for the promotion of comfortable deals and just shares, and not for the convenience of the state accountant. They were of a piece with those great inventions of English law - joint ownership (conceived as a ‘trust for sale’) and limited liability - inventions which instead of retarding enterprise, as those with rational minds imagine, put England a hundred years ahead of continental Europe in the search for industrial prosperity”.