All the Myriad Ways

Larry Niven’s classic science fiction short story “All the Myriad Ways” points out a problem with the Many-Worlds Interpretation of quantum mechanics: if there is no collapse of the quantum wave function, then all possibilities actually happen. That would seem to imply that we make all possible personal choices, including the really bad ones. This makes a mockery of our notions of free will, even worse than determinism: if we make all choices, then we really don’t exercise our will at all.

There is an obvious flaw in this argument: there is no particular reason to think that uncertainty at the quantum level leads to our making different choices. Most quantum events actually have no effect at the macroscopic level at which we live. If one entire molecule of oxygen tunnels across a room–an event which will occur at a vanishingly smal probability–nothing will change at the macroscopic level. And even if a bunch of molecules in my brain switch places, that doesn’t mean that I will change my mind about something.

Our actions are constrained by who we are. Quantum activity could conceivably make us into different people. It can’t make us be the same person who made a different decision.

Still, quantum mechanics in general, and the Many Worlds Interpretation in particular, pose some real philosophical problems. Unfortunately they don’t pose the problems addressed by science fiction novels about parallel worlds. The problems are more along the lines of what it is like to live in a world in which low probability events are not only possible but actually happen all the time.

Iain M. Banks, in his novel “The Algebraist,” argued that the only universal religion is one in which we assume that our universe is actually being simulated by an incomprehensibly large computer, and that our only meaningful goal is to try to reach the creator by proving that it really is a simulation. That seems as good a reason as any for why we never see low probability events in macroscopic universe: because the computer doesn’t bother to simulate them.