Last night I was out with some friends at a birthday celebration at our local pub, and– as often happens among people of a certain age– the conversation turned to back problems. I confessed that one of the great epiphanies of my life was the discovery that, after many hours of sitting (usually in terribly un-ergonomic positions) the way to deal with a sore back was to exercise, not to be sedentary. The lesson that exercise can be a cure for physical ailments became to basis of a more general assumption that we’re usually better off when we choose activity over inactivity– an idea that runs around in the subtext of REST.

These kinds of small but significant moments of enlightenment are often lost to history, in part because they sound mundane and slightly embarrassing: you’re supposed to have epiphanies on the road to Damascus, not in the gym. But this morning I found another example in John Maynard Keynes’ obituary of his Cambridge mentor, economist Alfred Marshall. (This is not as weird as it sounds: it’s a famously well-done piece of work. As the Wikipedia biography of Keynes notes, “Joseph Schumpeter called [it] ‘the most brilliant life of a man of science I have ever read.’ Marshall’s widow was ‘entranced’ by the memorial, while Lytton Strachey rated it as one of Keynes’s ‘best works’.”)

In the obituary, Keynes quotes Marshall’s account of an epiphany he had about the nature of work and rest:

An epoch in my life occurred when I was, I think, about seventeen years old. I was in Regent Street, and saw a workman standing idle before a shop-window: but his face indicated alert energy, so I stood still and watched. He was preparing to sketch on the window of a shop guiding lines for a short statement of the business concerned, which was to be shown by white letters fixed to the glass. Each stroke of arm and hand needed to be made with a single free sweep, so as to give a graceful result; it occupied perhaps two seconds of keen excitement. He stayed still for a few minutes after each stroke, so that his pulse might grow quiet. If he had saved the ten minutes thus lost, his employers would have been injured by more than the value of his wages for a whole day. That set up a train of thought which led me to the resolve never to use my mind when it was not fresh; and to regard the intervals between successive strains as sacred to absolute repose. When I went to Cambridge and became full master of myself, I resolved never to read a mathematical book for more than a quarter of an hour at a time, without a break.

I had some light literature always by my side, and in the breaks I read through more than once nearly the whole of Shakespeare, Boswell’s Life of Johnson, the Agamemnon of Aeschylus (the only Greek play which I could read without effort), a great part of Lucretius and so on. Of course I often got excited by my mathematics, and read for half an hour or more without stopping: but that meant that my mind was intense, and no harm was done.

You never know when inspiration will strike– or perhaps, you never know what apparently ordinary event can lead to some life-changing discovery.