Let’s leave philosophers to puzzle over the reality of numbers

The reality (or lack thereof) of numbers is the kind of problem some philosophers consider overwhelmingly important, but it’s of no consequence to just about everyone else. It does not make a wink of difference to your life whether the figures in your bank account or the digits on your clock are, in a philosophical sense, really real, so long as they work as expected. The mathematician Paolo Zellini’s book, now translated by Simon Carnell and Erica Segre from the 2016 Italian original, does not exactly elevate the number-reality problem to a matter of concern to non-philosophers, and certainly does not explain the problem in a way that will make it tractable to them. But Zellini does offer a creative shift in perspective that challenges certain philosophers and philosophy-minded mathematicians to see the problem differently.

Where one might expect numbers to get their reality from the things they enumerate — canonically, two apples come before the number two — Zellini argues that this gets the story backward.