The Power of Twelve & Twenty

Twelve and Twenty are interesting numbers. Although for the most part these days in the UK we use pretty much the base-10 metric system, with its apparently flawless internal structural logic, 'twas not always thus, as I've written about several times over the lifetime of this blog. Up until 1971, our national currency system was a largely duodecimal one, [base-12], albeit with the addition of the proto-decimal 'florin', equal to one tenth of a pound. But crucially, the pound was comprised of 240 pence, and so the florin actually equated to 24d [pence], or 2s [shillings]: a shilling being 12 pence or one twentieth of a pound. Clear so far?

The point of all this, as I've mentioned before, is that the divisibility of twenty and twelve is much greater than that of one hundred and ten. Whereas decimal chunks subdivide equally into chunks of two and five, twelve and twenty subdivide equally into two, three, four, six; and in the case of twenty, also five and ten: affording a practical granularity of whole numbers, without having to resort to further subdivision by fractions. All of these numbers are also manageable, human-scale numbers: we don't just have ten physical digits, but twenty, counting all four limbs, and again, four being a divisor of twelve and twenty. The old numbering systems were devised over millenia to reflect us as humans, and for the longest time were far more logical than the over-simplification of the decimal system.

For standardised scientific accuracy, the decimal system will always win out, but the fact is that being able - in normal life, at least - to work outside of the artificial strictures of the decimal system with its lack of real-world granularity, is of great benefit in practical terms. Ultimately it's about manageability and manipulability: counting based around twelve and twenty has a malleability that simply counting in tens can't match in human terms: a kilogram subdivides into grams: a stupidly large and small pairing in practical terms, unless you're weighing drugs, of course; although I guess there's also the decigram or centigram, but no-one ever thinks of those, and anyway, it's still a clunky way of subdividing without resorting to fractionation. Far better that we had the granularity of twelve and twenty to break things up into more visualisable chunks of weight: ounces, pounds, stones, hundredweights and tons, just to mention the larger subdivisions - I'll ignore parallel systems such as Troy, which had - has - more specialised applications, or the truly archaic stuff that probably needed to wither and pass on anyway [blog posts passim].

A person's weight measured in stones, is a practical and compact number, and subdivides neatly into pounds and ounces; without the nicety or need for a decimal point. A pound weight is the weight of a chunk of meat or vegetables that will feed a trencherman, or two normal people, at one sitting, itself dividing neatly into quarters and ounces. A hundredweight is the maximum load that a normal, fit human can carry, although health & safety - rightly - now dictates that approx. half that is acceptable. So a sack of coal or sand was measured as one hundredweight, or one twentieth of a ton, which in turn can easily be visualised as such. And so it goes on. As a mathematics teacher friend of ours once said back in the eighties, thinking in twelves and twenties encourages flexibility of mind and aids mental arithmetic, facilitating easy estimation. Chuck in the rote learning of multiplication tables - you don't need the theory of the underlying maths for any of it - and you have a pretty good and completely internalised survival toolkit to avoid being ripped off. It's not just nostalgia: it's just plain, common, human sense...