> However, there are reasons to believe that wavefunction collapse is an illusion brought on by something called decoherence. Decoherence itself doesn't explai

> However, there are reasons to believe that wavefunction collapse is an illusion brought on by something called decoherence. Decoherence itself doesn't explain the (apparent) wave-function collapse. Decoherence just tells you why the quantum states can't self-interfere after coming in contact with "the environment" (such as in a measurement). You still need to invoke some other explanation why the non-interfering states can't both be observed (or shut up and calculate). In MWI, this other explanation is the claim that "a classical observer" is an entity that only exists in one "branch" of the state space at one time, and can only perceive the solution to the wave equation they are entangled with. But this is an extra assumption entirely equivalent to the Born rule, though it is more intuitively acceptable in some way.