If many worlds is true and every choice happens somewhere, does choice matter?

[Jeffy]

The many worlds interpretation of quantum mechanics holds that every possible outcome of a quantum measurement actually occurs, each in its own separate, non-communicating branch of an ever expanding total universal wave function. Since human decisions ultimately bottom out in physical processes, and those processes are ultimately built from quantum events, a sufficiently strict reading of many worlds seems to imply that every genuinely possible choice you could make in any given moment is being made somewhere, in some branch, by some version of you that split off at that exact decision point.

That raises an immediate and genuinely uncomfortable question about whether ordinary moral responsibility and deliberation retain any of their usual meaning under those specific conditions. If some branching version of you is going to help a stranger regardless of what you personally decide right now, and some other branching version is going to walk past that same stranger without helping regardless as well, in what meaningful sense is this particular version of you, the one reading these words right now, actually making a real choice with genuine stakes attached to it.

One response distinguishes carefully between the existence of other branches and the reality of what happens to you specifically, within your own particular branch. Even if some other version of you elsewhere makes a different choice entirely, the specific version of you having this exact experience right now is the one whose actual decision determines what happens next along your own single continuous thread of experience. Under that view, branching does not obviously undermine responsibility any more than the mere existence of other people who make different choices already does in ordinary daily life.

A second, considerably more radical response bites the bullet directly and argues that moral responsibility genuinely was always somewhat illusory in a deterministic universe anyway, and many worlds simply makes that pre-existing tension newly vivid and impossible to ignore rather than actually introducing an entirely new problem into an otherwise clean picture. Compatibilists have spent centuries working out how responsibility can meaningfully survive determinism, and this specific scenario, viewed carefully, may not actually require anything conceptually new beyond that existing philosophical toolkit.

A third response simply questions whether many worlds is even the correct interpretation of quantum mechanics in the first place, sidestepping the entire problem by denying its central premise altogether. Given that the interpretation question remains genuinely, deeply unresolved among working physicists, tying an entire account of moral responsibility to one specific and contested reading of quantum mechanics might simply be building on ground that is nowhere near as stable as it needs to be to bear that much philosophical weight.