William Poundstone 2019. How to Predict Everything. London: Oneworld Publications, 306 pp.

Not as interesting as I thought it should have been, and not as interesting as I remember The Prisoner’s Dilemma being. The substantial content is thin: Bayes Theorem in the context of the Copernican Principle. The Copernican Principle is that any prediction or analysis that is based on an assumption that the observer occupies a special or priveliged position in a spectrum of possible values is flawed. The most likely place for the observer is a median position in any span (of time, for example). This is applied to such sobering topics as the likely remaining span of time expected for human civilisation and of the human race.

The most interesting parts are those that explore the ideas of J. Richard Gott III, which more Copernican than Bayesian: he concludes that there is a 95% chance of human extinction within 9,120 years. I found the explanation of this on wikipedia to be easier to follow than Poundstone’s. Probably because it is lighter on thought experiments which Poundstone uses so liberally that I found them tiresome by the end. But I’m going to read Gott in his own words soon, especially

Gott, J. Richard III 1993. Implications of the Copernican principle for our future prospects. Nature 363 (6427): 315–319.

Depending on one’s outlook, it is either a strength or a weakness of this line of argument that there is no consideration whatsoever of causal explanations of the events being predicted in this book; it is all purely empirical Bayesian probability theorising. I suppose the Butterfly-effect unpredictability of complex phenomena is a good argument for settling on an empirical approach.

Other valuable insights are that the likely lifetime (and profitable span for investors) of a company is best predicted by the present age of a company. Warren Buffet’s best 10 investment companies have ages of 234 and 42 years (only 2 are younger than 100 years and one of those is Apple).

Another appealing moment is the artwork that forms the frontispiece: Mark Tansey’s Achilles and the Tortoise. Poundstone has an engaging explanation but there are others.