[2/4] > Decoherence doesn’t explain, though, why the wavefunction collapses to a singular thing we call “reality”. So quantum mysticism still has room to flou

[2/4] > Decoherence doesn’t explain, though, why the wavefunction collapses to a singular thing we call “reality”. So quantum mysticism still has room to flourish. No. Decoherence is the thing that lets you avoid the need to collapse at all. The point of decoherence is that many quantum particles interacting together looks like a quantum superposition of many classical systems. So if you "are" one of those particles and look around, you'll see things behaving classically---only if you are "outside" (ie. have full access to the wf) can you see anything quantum going on. If the wavefunction doesn't collapse, why does it look like it does collapse?! Well, you're inside the wavefunction. Before the different classical possibilities decohere, you wait with anticipation. After decoherence, a version of you is in each branch of the wavefunction, each observing different outcomes, wondering how the wavefunction collapsed! But, it didn't---it's just hard to see that from where you're standing. This is the claim of the Many Worlds interpretation --- the wavefunction never collapses. Everything just evolves according to the Schrodinger equation, forever. There is no place or regime where quantum mechanics breaks down. Every branch of the wavefunction is equally real and continues to exist forever. So, why don't we see all sorts of zany, quantum effects in our every day life? Decoherence saves the day: even with a few dozen particles the different branches of the wavefunction have decohere enough that it'd take a massive, huge, gargantuan coincidence for two parts of the wavefunction to interfere. It's still possible! But it's extremely unlikely. Now scale up to Avogadro's number of particles, and forget it: things just look classical.