The multiverse is a popular theory in physics–especially quantum cosmology (or so I’ve read). Of course, it’s a controversial theory, but it’s a scientifically respectable and respected theory within the guild. Suppose we grant that theory for the sake of argument.
Let’s compare that with a stock objection to miracles: extraordinary claims demand extraordinary evidence. This goes back to Hume, although it was popularized by Sagan. Suppose we grant that objection for the sake of argument.
But doesn’t the multiverse moot Sagan’s objection? If the multiverse exists, then nothing is extraordinary. For if the multiverse exists, then every possibility is realized in some parallel reality or another. Every alternate possibility pops up in some corner of the far-flung multiverse. But in that case, every event is ordinary in the great scheme of things. Indeed, every event is equally ordinary. Nothing is too improbable to occur. Indeed, it’s inevitable.
So which gives–Sagan, or the multiverse?