Steve Jobs of the Renaissance? Keith Devlin's 'The Man of Numbers'

At the start of "The Man of Numbers", the subject of the book - Leonardo of Pisa - is compared to a pre-Renaissance Steve Jobs. Gratuitous and opportunistic? Not really. It's a clever - even canny - comparison admittedly, but spot on. Leonardo of Pisa is better known to us as 'Fibonacci' (a nicknamed coined by a 19th century historian), and as Keith Devlin rather skilfully explains in this beatifully produced book, he took a number system in existence for more than 700 years, optimised it for merchants, made it more user-friendly - and in doing so transformed the world.

The bare facts are these: the Hindu-Arabic number system has been existence for hundreds of years, but in medieval Europe it was of academic interest only, and everyone else got on with roman numberals and the abacus. Calculations - particularly for commerce - were carried out using arcane methods fiercely guarded by calculators, and a lot of trust was involved (no records of any of the working, you see?). Add to the fact that at that time there were a multitude of weights, measures, currencies and you get an idea of the complexities of trade.

Leonardo grew up as the son of a wealthy trader in Pisa, who thus had the education, the experience (through travelling in North Africa) and the opportunity to observe the power of the 'new math' at first hand, and realise the potential for simplifying trade. It is a measure of the ubiquity of the Hindu-Arabic system ("the only global language") that Devlin has to work hard to make us understand the profound implications of using base 10 numbers, of number placement, and of the 'tricks' that can be done to do complex calculations.

Leonardo's publication of Liber abbaci ("The Book of Calculation") was an immediate success, and its focus on being a teaching aid (with plenty of worked examples) ensured its widespread copying and dissemination. The impact was dramatic and rapid. Despite initial resistance to the number system (you can imagine the power-position that existing calculators occupied and their Luddite response) its potential to manage increased complexity meant the new maths was unstoppable, and led to developments in trading, banking, ledger-keeping, and more complex companies based on pooled capital or 'shares'. This was something that turbo-charged Italy's place as the centre of global commerce.

The fact that history has forgotten Leonardo (Fibonacci comes from the moniker 'Fils Bonacci', or son of the Bonacci family) is both surprising and intriguing, although Devlin does some superb detective work to make plausible suggestions of why this was. It provides a primer on the history of mathematics and numbers, pre-eminent Muslim scholars, pre-Renaissance Italian politics and business, medieval manuscript hunting and even the impact of the printing press.

It must be said, "there is maths in this book". This requires some engagement from the reader, and at least one chapter will require you to put aside any school-era squeamishness to see the examples that would have had such a big impact. But it's worth it. And I think Mr Jobs would have been flattered by the comparison. Although there is a little sting in the tale: in an era before the printing press, widespread copying of the original manuscript - and an explosion of copycat publications - ensured that Leonardo all but disappeared from the historical record, and his only recently (through painstaking computer-aided analysis) been returned to his rightful place.
Republished again in Italian only in the 1800s, with an English language translation only published in 2002, the rescuing of Fibonnacci’s reputation and standing in the development of maths has been a long time coming. With this book, there is a hope that a much wider audience will learn about - and appreciate - what Leonardo of Pisa achieved.