  There is a persistent confusion about determinism and predictability. In
spite of the opinions of some eminent philosophers (e.g., Popper), it is
possible to understand that the two concepts are completely unrelated. In few
words we can say that determinism is ontic and has to do with how Nature
behaves, while predictability is epistemic and is related to what the human
beings are able to compute. An analysis of the Lyapunov exponents and the
Kolmogorov-Sinai entropy shows how deterministic chaos, although with an
epistemic character, is non subjective at all. This should clarify the role and
content of stochastic models in the description of the physical world.
