if the mark of a serious scientific theory is its breadth of application, its explanatory power, its quantitative accuracy, and its ability to make novel predictions, then it is hard to think of a theory more “worth taking seriously” than quantum mechanics. So it seems entirely apposite to ask what ontological claims quantum mechanics makes, if taken literally, and to take those claims seriously in turn.
And quantum mechanics, taken literally, claims that we are living in a multiverse: that the world we observe around us is only one of countless quasi-classical universes (“branches”) all coexisting… if the theory is worth taking seriously, we should take the branches seriously too.
If you’re acquainted at all with the P=NP problem, this is an amazingly read. A shame I couldn’t find a great quote to summarize it.