Laplace’s Demon

The following extract is taken from Nate Silver‘s excellent book ‘The Signal and the Noise’. In it he introduces the philosophical position of Pierre-Simon Laplace known as Laplace’s Demon.

“The debate about predictability began to be carried out on different terms during the Age of Enlightenment and the Industrial Revolution. Isaac Newton’s mechanics had seemed to suggest that the universe was highly orderly and predictable, abiding by relatively simple physical laws. The idea of scientific, technological, and economic progress—which by no means could be taken for granted in the centuries before then— began to emerge, along with the notion that mankind might learn to control its own fate. Predestination was subsumed by a new idea, that of scientific determinism.

The idea takes on various forms, but no one took it further than Pierre-Simon Laplace, a French astronomer and mathematician. In 1814, Laplace made the following postulate, which later came to be known as Laplace’s Demon:

“We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes.”

To summarise: with perfect knowledge we ought to make perfect predictions.

This, however, seems to be a purely theoretical position.

Laplace and Silver concede as much. Perhaps this is why the observation is known as his demon.

Some systems are too complex, and too tightly coupled, to fully understand.

At least for humans.

Philip Tetlock’s work on the limits of expertise illustrate this point perfectly.

Even the predictions of experts, with more information than ever, rarely outperform guesses, when working in complex fields.

Hey. I’m Alex Murrell. I'm a Planner at Epoch Design in Bristol where I help deliver highly creative, innovative and effective pack, instore and online communications for some of the world’s biggest FMCG brands. Want to know more? You can find me on Twitter or LinkedIn.

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