Stephen Wolfram on Computational Irreducibility

…I strongly suspect…that in the vast majority of cases where the behavior that we see in nature and elsewhere appears to us complex it is in the end indeed associated with computational irreducibility. …
In the past it has normally been assumed that there is no ultimate limit on what science can be expected to do. …it has become common to think that eventually it should yield an easy theory —perhaps a mathematical formula —for almost anything.
But…computational irreducibility…implies that this can fundamentally never happen, and that in fact there can be no easy theory for almost any behavior that seems to us complex.

—Stephen Wolfram https://www.wolframscience.com/nks/chap-12–the-principle-of-computational-equivalence#sect-12-6–computational-irreducibility

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Stephen Wolfram on Combinators