From Samir Varma, Cos Cob, Connecticut, US
Howie Firth posed a superb scenario related to the question of whether we have free will: “If every action we make is predetermined by the laws of physics, then it is possible to imagine constructing a computer that could predict what I will do at a particular moment”. He then suggests that, knowing its prediction, he could simply choose to do something else(Letters, 12 July).
Having written a book about this, the short answer is that you can’t build such a computer, even though the laws of physics are deterministic. There are three fundamental reasons: complexity (the sheer number of variables); chaos (sensitivity to initial conditions); and, most importantly, computational irreducibility – even simple rules can produce outputs that can’t be predicted without running the entire computation. It is precisely this lack of predictive ability that constitutes what I call “free will in practice”. This form of free will not only exists, but must exist, even in a deterministic universe.
