The interpretational landscape

Context

The quiet decades. After 1927 the Copenhagen view hardened into orthodoxy, and questioning it became a career risk. David Bohm found that out in 1952: his hidden-variable reconstruction of quantum mechanics — a live counterexample to the folklore that no such theory could exist — landed while he was being driven out of Princeton by McCarthyism, and the combination buried it; he did the work in exile in Brazil. Hugh Everett III fared no better in 1957: his "relative state" formulation (no collapse; the universal wave function branches) was cut to a fraction of its length under Wheeler's editing to avoid offending Bohr, was dismissed in Copenhagen anyway, and Everett left physics for defense work, dying before "many-worlds" became respectable. The era's unofficial motto — Mermin's phrase — was "shut up and calculate."

The reopening. Three things ended the silence. Bell's theorem made foundations experimental. Decoherence (Zeh, then Zurek) explained why superpositions hide from us — the environment measures everything constantly — without settling what remains. And spontaneous-collapse models (GRW, 1986) showed you could modify the dynamics itself and be testably different. By the 1990s, quantum information had made foundations fashionable; by 2012 the PBR theorem was constraining what "the wave function is just knowledge" views can coherently claim.

The landscape now. As of 2026 the field holds a genuinely plural set of interpretations — Copenhagen's descendants, Bohmian mechanics, Everett, collapse models, QBism, relational QM — each with proponents, critics, and theorems it must absorb. Every one of them is, at bottom, an answer to four questions: Is the wave function real or bookkeeping? Does collapse happen? Are there hidden variables? Is the theory local? Carry those four as a scoring rubric through every book and video in this unit; they turn a zoo into a table.

How to read it

Anchor. Travis Norsen, Foundations of Quantum Mechanics. The single best textbook for this goal — Norsen is a Bohmian sympathetic to realism, writes clearly, and is fair to every camp. Chapters 1–8 cover the whole unit. ~30 hours.

Paired primary readings (chapters only). John Bell, Speakable and Unspeakable in Quantum Mechanics — read "Bertlmann's Socks and the Nature of Reality" and "Against Measurement"; two reshaping essays, ~3 hours. David Wallace, The Emergent Multiverse — introduction and chapter 1 for the best Everettian exposition. Optional: Tim Maudlin, Philosophy of Physics: Quantum Theory — dense but the cleanest single overview; can substitute for Norsen.

Video lectures instead of more books (Theories of Everything channel): Maudlin (realist/Bohmian, sharp), Fuchs (QBism), Rovelli (relational), Adlam (balanced), Aaronson (information view, cuts fog), Wallace (Everettian). Sean Carroll's Mindscape solo episodes on Many-Worlds are the clearest MWI audio.

The four theorems — do not skip. Bell (1964): no local hidden variables. Kochen–Specker (1967): no non-contextual hidden variables. PBR (2012): under modest assumptions the wave function is ontic. Frauchiger–Renner (2018): "no single-world interpretation is consistent" — contested, subtle, important. Read summaries (Quanta, SEP); you need what each rules out, not the proofs.