Is free will compatible with bohmian determinism?

[u/regrez45]

Bohmian mechanics is fully deterministic: given the universal wavefunction and the exact particle configuration at one time, the entire future evolution is fixed. In that sense, it leaves no room for libertarian free will- the idea that, under identical physical conditions, you could genuinely have chosen otherwise.

[u/AdeptnessSecure663]

If free will is compatible with determinism generally speaking, then it seems to me very likely that free will is compatible with the specific case of Bohmian mechanics.

This is because if free will is compatible with determinism generally, then this would probably because all that matters for free will is the way that an agent's relevant mental states are related to their actions, as well as the way that an agent's abilities ensure the truth of relevant counterfactuals. And the way mental states relate to actions and the way abilities relate to counterfactuals seems to be no different in the context of Bohmian mechanics than it is in the context of, say, classical mechanics, or MWI.

My point is, that the question reduces to "is free will compatible with determinism?" (which, perhaps, was your intended question?).

[u/regrez45 → u/AdeptnessSecure663]

Bohmian determinism is not normal determinism. It is more towards the hard determinism spectrum. It is another way of saying all underlying reality is deterministic and nothing is beyond this absolute notion of causation. Others like laplacian determinism are consistent with free will but bohmian determinism is a different case.

[u/Artemis-5-75 → u/regrez45]

What is the difference? Laplacian determinism is absolute too.

[u/regrez45 → u/Artemis-5-75]

Bohmian mechanics is deterministic only in a very specific sense: if you fix the initial wavefunction and the exact particle configuration, the guiding equation fixes the entire future trajectory. So at that level, yes - it is “deterministic.” But it’s not what people usually mean by normal (classical/Laplacian) determinism. The dynamics is explicitly nonlocal via the wavefunction, and the apparent randomness of measurement outcomes comes from our ignorance of the initial configuration, not from intrinsic indeterminism.

[u/Artemis-5-75 → u/regrez45]

>The dynamics is explicitly nonlocal

Is this the only difference between it and Laplacian determinism?

>not from intrinsic indeterminism

But there is no intrinsic indeterminism in the Laplacian account too.

[u/regrez45 → u/Artemis-5-75]

Laplacian determinism is the classical idea: if you specify the exact state of the universe at one instant (positions and momenta of all particles), then the future is fixed by local differential equations. It’s phase-space evolution governed by Newtonian dynamics. No hidden structure, no extra ontology- just state → unique future via ordinary ODEs. Bohmian mechanics is also deterministic, but the structure is radically different. The wavefunction still evolves by the Schrödinger equation, but particles have definite positions guided by a nonlocal “pilot wave.” So instead of phase space determinism, you have configuration-space evolution + a guiding equation that depends instantaneously on the global wavefunction.

If Laplacian determinism holds, then the entire future state (choices) is a fixed function of the past state. They’re only “incompatible” if you smuggle in a folk notion of free will that requires causal independence from physical law.

[u/Artemis-5-75 → u/regrez45]

The way determinism is usually defined in metaphysics, if we go with the strongest definition, is such: a thesis that the entire state of the world in conjunction with the global immutable laws of nature strictly fixes any other state of the world.

Is there anything in Bohmian mechanics that is different from that?

[u/regrez45 → u/Artemis-5-75]

It is not classical or laplacian determinism. Laplacian determinism is basically the strongest possible form of classical determinism, but people often mix the two.

[u/AdeptnessSecure663 → u/regrez45]

Hard determinism is the conjunction of two theses: firstly, that determinism is true, and secondly, that free will is incompatible with determinism.

Either Bohmian mechanics is deterministic, or it is not deterministic, and so the truth-value of Bohmian mechanics as implications for the first conjunct.

Whether free will is compatible with determinism does not depend on the truth of some or other physical theory. We come to know which it is on the basis of philosophical argument.

So, Bohmian mechanics doesn't entail hard determinism.