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If we look at the way the universe behaves, quantum mechanics gives us fundamental, unavoidable indeterminacy, so that alternative histories of the universe can be assigned probability.

"THE SIMPLE AND THE COMPLEX Part I: THE QUANTUM AND THE QUASI-CLASSICAL with MURRAY GELL-MANN, Ph.D". Interview with Jeffrey Mishlove, www.intuitionnetwork.org.
If we look at the way the universe behaves, quantum mechanics gives us fundamental, unavoidable indeterminacy, so that alternative histories of the universe can be assigned probability.