2. The Two Things game

Each day in the run-up to Christmas, we present an extract from Barnaby Rogerson's fascinating Book of Numbers. Today, our festive countdown reveals that any discipline can be boiled down to two basic principles

[1] People love to play the Two Things game, but rarely agree about what the two things are. [2] That goes double for anyone who works with computers.

A few years ago, Glen Whitman was chatting with a stranger in a Californian bar. When he confessed to this stranger that he taught economics, the drinker replied without so much as a pause for breath, "So what are the two things about economics? You know, for every subject there are really only two things you really need to know. Everything else is the application of those two things, or just not important."

"Okay," said the professor. "One: Incentives matter. Two: There's no such thing as a free lunch."

Inspired, Glen started playing the Two Things game and recording some of the results on a web page (Google "Whitman" and "Two Things" and you'll get there). But it's more fun to try it for yourself – and especially good if you find yourself at a dinner next to a self-important professional. Here are some of the best of Whitman's:

Finance: [1] Buy low. [2] Sell high.
Medicine: [1] Do no harm. [2] To do any good, you must risk doing harm.
Journalism: [1] There is no such thing as objectivity. [2] The end of the story is created by your deadline.
Theatre: [1] Remember your lines. [2] Don't run into the furniture or fall off the stage.
Physics: [1] Energy is conserved. [2] Photons (and everything else) behave like both waves and particles.
Religion: [1] Aspire to love an unknowable god. [2] Do this by trying to love your neighbour as much as yourself.

Tomorrow: tricolons.

• Taken from Rogerson's Book of Numbers by Barnaby Rogerson (Profile).

Reference and languagesEconomicsBarnaby Rogerson
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