= Causality in quantum mechanics
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In simple terms, if you believe in the <Schrödinger equation> and its modern probabilistic interpretation as described in the <Schrödinger picture>, then at first it seem that there is no strict causality to the outcome of experiments.
People have then tried to recover that by assuming that there is some inner sate beyond the <Schrödinger equation>, but these ideas are refuted by <Bell test experiments>, unless we give up the <principle of locality>, which feels more important, especially in <special relativity>, where <faster-than-light implies time travel>, which breaks causality even more dramatically.
The <de Broglie-Bohm theory> is a deterministic but <non-local> formulation of quantum mechanics.