Is Kant's project of reconciling freedom with an apparently deterministic nature still relevant given how Quantum mechanics does not (as I understand it) see nature as a deterministic totality?

In my opinion, it's no harder to reconcile freedom (free choice, responsible action) with determinism than to reconcile it with indeterminism. On the contrary, it may be easier; see, for example, this SEP entry. According to compatibilists, we can act freely even if determinism should turn out to be true and hence even if the indeterministic interpretation of quantum mechanics should turn out to be false. But no one thinks that the truth of indeterminism (whether quantum indeterminism or some other kind) by itself would suffice to give us freedom. The debate is about whether indeterminism is necessary for freedom. In my view, incompatibilists bear the burden of showing that it is and have failed to discharge that burden.

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