People crave specific knowledge of the evolution of complex systems, paying good money for the services of clairvoyants and economic forecasters. But such knowledge is rarely available. Nor, even if it were available, would it often be useful. Physicists studying sport have established that many fieldsmen are very good at catching balls, but bad at answering the question: ???Where in the park will the ball land???? Good players don???t forecast the future, but adapt to it. That is the origin of the saying ???keep your eye on the ball???.

As complex systems go, the interaction between the ball in flight and the moving fieldsman is still relatively simple. In principle, most of the knowledge needed to compute trajectories and devise an optimal strategy is available: we just don???t have the instruments or the time for analysis and computation. More often, the relevant information is not even potentially knowable. The skill of the sports player is not the result of superior knowledge of the future, but of an ability to employ and execute good strategies for making decisions in a complex and changing world. The same qualities are characteristic of the successful executive. Managers who know the future are more often dangerous fools than great visionaries.

Most people who hire fortune tellers have the good sense to treat their prognostications lightly. The activity is casual fun, its value ??? if any ??? is as provocation to think carefully about the present rather than a measure of gaining knowledge about the future. Good predictions may be available in structured, well-ordered, situations ??? but, even then, forecasts are properly conditional or probabilistic. There are few certainties about the future: but one is that hedgehogs who make confident statements on the basis of some universal theory will be as persistently misleading counsellors in the future as in the past. And that the foxes, like Mr Silver, who scramble everywhere for scraps of information will provide better, if more nuanced, advice.