Physics is my religious belief. In the sense that in physics we discover a fantastically wonderful world out there that’s rich in potential, rich in … - Frank Wilczek

If the “universe” contains everything that exists, what can be outside it? If the answer is “Things that don’t exist”, then “multiverse” becomes an idea in the domain of psychology, not physics.

Ironically, conventional quantum mechanics itself involves a vast expansion of physical reality, which may be enough to avoid Einstein Insanity. The equations of quantum dynamics allow physicists to predict the future values of the wave function, given its present value. According to the Schrödinger equation, the wave function evolves in a completely predictable way. But in practice we never have access to the full wave function, either at present or in the future, so this “predictability” is unattainable. If the wave function provides the ultimate description of reality — a controversial issue! — we must conclude that “God plays a deep yet strictly rule-based game, which looks like dice to us.”

The “Copernican Principle” or “Cosmic Mediocrity”... states, basically, that Earth does not occupy a privileged place in the universe. Universality asserts more, namely that there are no privileged places or times.