Why do some scientists criticize multiverse theories as speculation rather than science?

Scientists often criticize multiverse theories as speculation rather than science because they frequently lack empirical verification, which is a cornerstone of the scientific method. A primary concern is the criterion of falsifiability, which posits that for a theory to be considered scientific, it must be possible in principle to prove it false through observation or experimentation.12

Critics argue that many multiverse models, particularly those that are highly disconnected, do not offer testable predictions, rendering them more akin to philosophy or metaphysics than empirical science. Furthermore, some researchers invoke Ockham’s razor, suggesting that proposing the existence of other universes multiplies entities beyond necessity when simpler explanations might suffice.12

Debates also persist regarding the use of anthropic arguments to explain physical constants. While some view these as valid, others argue they are difficult to quantify and may discourage the search for more elegant, testable physical explanations.1