Steam engine entrepreneur James Watt, as responsible as anybody for upgrading the world from poor to rich, left a notebook of his work. Squiggly symbols such as “5” and “2” mark the pages. Without these little glyphs, borrowed by Europeans from medieval Arabs, Watt would not have been able to determine cylinder volumes, pressure forces, and heat-transfer rates. Isaac Newton would’ve struggled to find that gravity is inversely proportional to the square of a planet’s distance from the sun. Calculations for Antoine Lavoisier’s chemistry, Abraham de Moivre’s probability tables, and the Bank of England’s bookkeeping would have been difficult or impossible.
But before Hindu-Arabic numerals could fuel the Enlightenment and the Industrial Revolution, society had to start to think quantitatively. Jessica Marie Otis’ By the Numbers is about scribes starting to write 7 instead of VII, parish clerks counting plague deaths rather than guessing, and gamblers calculating instead of hoping and praying.
Why did some countries become wealthy after 1800? Historians argue about the relative influences of religion, climate, geography, slavery, colonialism, legal systems, and natural resources. But the key, famously shown by economist Robert Solow, who died in December, is technological innovation enabling more and more goods and services to be produced per worker and unit of capital. Innovation needs research, development, and engineering. All those require numbers and numeracy.