Why do critics describe some multiverse theories as philosophy rather than science?

Critics often categorize certain multiverse theories as philosophy rather than science because they lack the criterion of falsifiability, a foundational standard in the philosophy of science which holds that a theory is only scientific if it is possible in principle to prove it false.12

The primary concerns regarding the scientific status of multiverse models include:

• Lack of Empirical Verification: Many multiverse theories, particularly those involving disconnected universes, do not offer clear ways to conduct experiments or make observations that could confirm or refute their existence.1
• Ockham’s Razor: Critics argue that invoking an infinite number of unobservable universes violates Ockham’s razor, which suggests that the simplest explanation for a phenomenon is generally preferred.1
• Anthropic Reasoning: The use of anthropic arguments—suggesting our universe has specific physical constants because they are necessary for life—is often viewed as difficult to quantify or test, leading some to view it as a non-scientific explanation.1

While some models, such as those derived from inflation, are grounded in testable physics, the more disconnected versions remain speculative.1