From Jim Baggott at Prospect:
Over the last few decades “multiverse theories” have become increasingly fashionable within a relatively small—but publicly vocal—group of theoretical physicists. This group specialises in foundational problems in cosmology, particle physics, and quantum mechanics. These theories are advertised as science’s answer to much that we can’t otherwise explain about the universe we inhabit, the elementary particles we have discovered in it, and the reasons for our own existence.
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The first victim is context. For example, in a recent post to this blog, Philip Ball reports on a paper published by a team of astrophysicists in the “Monthly Notices of the Royal Astronomical Society.” Ball reports on this paper with an accuracy entirely consistent with his reputation as one of Britain’s best science writers, but it so happens that the paper is not about multiverse theory. And yet “multiverse theory” appears in the title. On publication, Prospect magazine tweeted a link with a caption that refers to “new ‘multiverse’ calculations,” implying that this is all about a real scientific multiverse theory, with the capacity to perform calculations (and, by association, make predictions) when multiverse theory actually can’t do any of this. This kind of thing helps to compound the deception, normalising multiverse theory as validated science. More.
The multiverse is believed and promoted without evidence precisely because it is not science. It is a philosophical stance against seeing any significance in the features of our own our universe. That doesn’t require evidence, just the ability to generate media-friendy theories, using the trappings of theoretical physics.
See also: A skeptic’s take on the latest multiverse hype at New Scientist
The Big Bang: Put simply, the facts are wrong.
What becomes of science when the evidence does not matter?
and
The multiverse is science’s assisted suicide