Reality is best explained by taking our best theories literally

Deutsch opens with a methodological complaint: physicists routinely use quantum theory to build working technology while refusing to believe what the theory's equations actually say about reality. He argues this is intellectually inconsistent — if a theory makes astonishingly accurate predictions and no better alternative exists, we owe it the same literal belief we'd extend to any other well-tested explanation, rather than treating it as a calculating trick we pragmatically tolerate. Retreating into "it's just math, don't ask what it means" is, in his view, an abdication of the entire purpose of science, which is to explain the world, not merely predict it. This stance sets up his willingness to accept conclusions, like multiple universes, that common sense finds absurd. Takeaway: refusing to follow evidence to uncomfortable conclusions isn't caution — it's a failure of explanation.