Laplace's Demon - Recent Views

Recent Views

There has recently been proposed a limit on the computational power of the universe, i.e. the ability of Laplace's Demon to process an infinite amount of information. The limit is based on the maximum entropy of the universe, the speed of light, and the minimum amount of time taken to move information across the Planck length, and the figure was shown to be about 10120 bits. Accordingly, anything that requires more than this amount of data cannot be computed in the amount of time that has elapsed so far in the universe.

Another theory suggests that if Laplace's demon were to occupy a parallel universe or alternate dimension from which it could determine the implied data and do the necessary calculations on an alternate and greater time line the aforementioned time limitation would not apply. This position is for instance explained in David Deutsch's The Fabric of Reality, who says that realizing a 300-qubit quantum computer would prove the existence of parallel universes carrying the computation.

It must be admitted that the openness of the future would be hard to defend in the rigidly deterministic universe that Laplace regarded as the inexorable consequence of taking Newtonian ideas seriously. We have seen that in that world, full knowledge of the present, together with unlimited calculating power, implies total knowledge of a rigorously entailed past and future. Nothing really novel ever happened; history was a reiterated tautology. However, the iron grip of Laplace's calculating demon has been relaxed by the twentieth century discovery of widespread intrinsic unpredictabilities present in nature, both at the microscopic level of quantum events and also at the macroscopic level of the behavior of exquisitely sensitive chaotic systems. We have noted already that the question of whether these epistemological deficiencies are to be interpreted as signs of an ontological openness is a metaphysical issue, not to be settled by the natural sciences alone. In the case of chaotic systems, we have seen that it is possible to develop an interpretation that leads to the existence of extra causal principles with the form of the 'active information', and that these might well be capable of accommodating the action of both human and divine agency. Such a programme would then achieve Pannenberg's desired defense of the openness of history, as theology wishes to understand it, not by appeal to field theory but to the ideas of the top-down effects of active information. There is much that is necessarily speculative here, but I believe that these ideas afford a better model than field for the presence and activity of the Spirit. —John Polkinghorne, Faith, Science and Understanding