# Why Quantum Mechanics states that nature is probabilistic? [duplicate]

I am new here and I am studying the philosophical implications of Quantum Mechanics. I read somewhere that QM and determinism are mutually exclusive and that QM involve a number of philosophers to think that nature is probabilistic. Is this true? And what are the theories or physical laws (in QM)that state that nature is probabilistic? In other words, where is the modal aspect in QM?

• QM, as a mathematical formalism, and determinism are not mutually exclusive, the standard (Copenhagen) interpretation of QM (and many others) and determinism are mutually exclusive. What suggests indeterminism is that, unlike classical physics, quantum mechanics only predicts distributions of outcomes. There are deterministic interpretations of QM, e.g. Bohmian mechanics, although they are, arguably, "artificial" because the deterministic hidden variables are undetectable. Many consider even the Many Worlds interpretation "deterministic", although it is a quaint kind of determinism Apr 11, 2019 at 18:44
• Thanks @Conifold. I am ignorant on the theme and I just started with it. For this reason, Could you clarify me why QM as mathematical formalism and determinism are not mutually exclusive? Are you saying that the mathematical equations and formulas of QM express a certain kind of determinism?Thanks for the help. Apr 11, 2019 at 20:29
• Moreover, are the mathematical formalism of QM and determinism never mutually exclusive? @Conifold Apr 11, 2019 at 20:32
• Mathematical formalism (with some minimal interpretation relating numbers to meter readings) expresses nothing by itself, so it can not exclude anything philosophical. Abstract generalizations, like realism, determinism, materialism (or lack thereof) require postulates way beyond the formalism. Some weaker relations can be argued, like "suggests" indeterminism, or makes it "more plausible", the way classical mechanics made determinism more plausible (because it made unique predictions for any initial values), see QM vs determinism thread. Apr 11, 2019 at 20:43