The Multiverse Is a Scientific Theory

The multiverse is a scientific theory but only if you are precise about which version of it you are talking about not all multiverses are equal in epistemology. We are in the realm now of pure abstract speculation metaphysics not science and while it can be fun to speculate it's more fun to know what you're doing. The dividing line is between good explanations and easy to vary accounts and between testable claims and non-science. This is likewise a metaphysical and not a scientific claim as it cannot be tested.