# The Man of Numbers: How Fibonacci Changed the World

Imagine a day without numbers — how would you know when to wake up, how to call your mother, how the stock market is doing, or even how old you are? We live our lives by numbers. They’re so fundamental to our understanding of the world that we’ve grown to take them for granted. And yet it wasn’t always so. Until the 13th century, even simple arithmetic was mostly accessible to European scholars. Merchants kept track of quantifiables using Roman numerals, performing calculations either by an elaborate yet widespread fingers procedure or with a clumsy mechanical abacus. But in 1202, a young Italian man named Leonardo da Pisa — known today as Fibonacci — changed everything when he wrote Liber Abbaci, Latin for Book of Calculation, the first arithmetic textbook of the West.

Keith Devlin tells his incredible and important story in The Man of Numbers: Fibonacci’s Arithmetic Revolution, tracing how Fibonacci revolutionized everything from education to economics by making arithmetic available to the masses. If you think the personal computing revolution of the 1980s was a milestone of our civilization, consider the personal computation revolution. And yet, Leonardo’s cultural contribution is hardly common knowledge.

The change in society brought about by the teaching of modern arithmetic was so pervasive and all-powerful that within a few generations people simply took it for granted. There was no longer any recognition of the magnitude of the revolution that took the subject from an obscure object of scholarly interest to an everyday mental tool. Compared with Copernicus’s conclusions about the position of Earth in the solar system and Galileo’s discovery of the pendulum as a basis for telling time, Leonardo’s showing people how to multiply 193 by 27 simply lacks drama.” ~ Keith Devlin

Though “about” mathematics, Fibonacci’s story is really about a great number of remarkably timely topics: gamification for good (Liber abbaci brimmed with puzzles and riddles like the rabbit problem to alleviate the tedium of calculation and engage readers with learning); modern finance (Fibonacci was the first to develop an early form of present-value analysis, a method for calculating the time value of money perfected by iconic economist Irving Fisher in the 1930s); publishing entrepreneurship (the first edition of Liber Abbaci was too dense for the average person to grasp, so da Pisa released — bear in mind, before the invention of the printing press — a simplified version accessible to the ordinary traders of Pisa, which allowed the text to spread around the world); abstract symbolism (because numbers, as objective as we’ve come to perceive them as, are actually mere commonly agreed upon abstractions); and even remix culture (Liber Abbaci was assumed to be the initial source for a great deal of arithmetic bestsellers released after the invention of the printing press.)

Above all, however, Fibonacci’s feat was one of storytelling — much like TED, he took existing ideas that were far above the average person’s competence and grasp, and used his remarkable expository skills to make them accessible and attractive to the common man, allowing these ideas to spread far beyond the small and self-selected circles of the scholarly elite.

A book about Leonardo must focus on his great contribution and his intellectual legacy. Having recognized that numbers, and in particular powerful and efficient ways to compute with them, could change the world, he set about making that happen at a time when Europe was poised for major advances in science, technology, and commercial practice. Through Liber Abbaci he showed that an abstract symbolism and a collection of seemingly obscure procedures for manipulating those symbols had huge practical applications.” ~ Keith Devlin

NPR has an excerpt, or you can sample The Man of Numbers on your Kindle:

UPDATE: Per Devlin’s comment below, there’s a complementary ebook titled Leonardo and Steve, drawing a compelling parallel between Fibonacci and Steve Jobs. If that isn’t already irresistible, the title goes for just \$2.99 — now could one resist?

Published July 21, 2011

https://www.themarginalian.org/2011/07/21/the-man-of-numbers-keith-devlin-fibonacci/

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