Scriven’s paradox of predictability arises from the combination of two ideas: first, that everything in a deterministic universe is, in principle, predictable; second, that it is possible to create a system that falsifies any prediction that is made of it. Recently, the paradox has been used by Rummens and Cuypers to argue that there is a fundamental difference between embedded and external predictors; and by Ismael to argue against a governing conception of laws. The present paper defends a new diagnosis (...) of the roots of the paradox. First, it is argued that the unpredictability has to be understood in the light of Turing’s famous results about computability, in particular his proof that there is no solution to the ‘halting problem.’ This allows us to see that previous analyses of the paradox were either mistaken or not fully adequate. Second, the sense of paradox that nevertheless remains is traced to the idea that rational behaviour is not dependent on contingent environmental circumstances: that it is always up to us to engage in activities such as rational prediction or rational belief. The paradox of predictability teaches us that this idea, natural though it may be, is mistaken. (shrink)

The inference from determinism to predictability, though intuitively plausible, needs to be qualified in an important respect. We need to distinguish between two different kinds of predictability. On the one hand, determinism implies external predictability , that is, the possibility for an external observer, not part of the universe, to predict, in principle, all future states of the universe. Yet, on the other hand, embedded predictability as the possibility for an embedded subsystem in the universe to make such predictions, does (...) not obtain in a deterministic universe. By revitalizing an older result—the paradox of predictability —we demonstrate that, even in a deterministic universe, there are fundamental, non-epistemic limitations on the ability of one subsystem embedded in the universe to predict the future behaviour of other subsystems embedded in the same universe. As an explanation, we put forward the hypothesis that these limitations arise because the predictions themselves are physical events which are part of the law-like causal chain of events in the deterministic universe. While the limitations on embedded predictability cannot in any direct way show evidence of free human agency, we conjecture that, even in a deterministic universe, human agents have a take-it-or-leave-it control over revealed predictions of their future behaviour. (shrink)

A few philosophers have held that determinism should lead to an attitude of resignation: since what will be will be, there is no point trying to influence the future. That argument has rightly been seen as mistaken. But a plausible parallel argument leads from the thesis of predictability---the thesis that it can be known what will happen---to an attitude of resignation. So if predictability is true, our normal practical attitudes may well be deeply mistaken. Fortunately, whilst determinism is a plausible (...) doctrine, there is a strong argument against predictability. Determinism and predictability should be kept well apart. (shrink)

This paper examines commonly offered arguments to show that human behavior is not deterministic because it is not predictable. These arguments turn out to rest on the assumption that deterministic systems must be governed by deterministic laws, and that these give rise to predictability "in principle" of determined events. A positive account of determinism is advanced and it is shown that neither of these assumptions is true. The relation between determinism, laws, and prediction in practice is discussed as a question (...) in scientific epistemology. (shrink)