The History That Happens

The real-world notes behind A Generalisation of Quantum Mechanics. The Archive names nobody from our century; the names are here, and nothing in lore changes. The first of two entries from one question on 28 September 2026; the second is The Third Sum Rule.

The question came plainly: which interpretation of quantum mechanics, if any, consistent with M-theory, best fits the Grand Ensemble? An interpretation is an account of what the formalism is about that changes none of its predictions. M-theory chooses none. What "consistent with M-theory" can honestly mean is four things: it must work for a closed universe with no observer outside it, add no dynamics of its own, respect relativity, and tolerate a landscape of possible vacua. That narrows the field before the record says a word, and the record then says several.

The record has already ruled most of them out. The Cascade holds that the future is genuinely open, that possibility resolves at the present once and without remainder, and that the past is static. Hugh Everett's many-worlds, in which every outcome happens and nothing resolves, is refused twice over, since branching futures are not the Ensemble. David Bohm's pilot wave puts a fact of the matter in place before the present arrives, and so denies the open future. The objective-collapse theories of Ghirardi, Rimini and Weber, and Roger Penrose's gravitational reduction, keep the open future but pay for it by amending the Schrödinger equation, and the record's kernel is standard quantum mechanics preserved exactly, extension and never deformation. John Cramer's transactional reading needs a backward-in-time handshake, which is refused. And a reading that lets consciousness cause collapse fails the plainest rule of all: an observation is any interaction that leaves a record, a photographic plate included.

What survives is consistent histories. Robert Griffiths proposed it in 1984, Roland Omnès developed it, and Murray Gell-Mann and James Hartle rebuilt it in 1990 for quantum cosmology under the name decoherent histories. A history is a sequence of yes-or-no questions asked of a system at successive times. A family of histories is consistent when the interference between its members vanishes, which is what decoherence, the leaking of phase information into an environment, brings about; the probabilities of a consistent family then add as ordinary probabilities do. Nothing outside the system is needed, which is why it is the framework Stephen Hawking and Hartle worked in, and it adds no dynamics: the kernel stays exact. In Griffiths's reading exactly one history from the family occurs and the rest were possibilities that carried probability, which is the Cascade's asymmetry in other words. Gell-Mann and Hartle lean toward treating every decoherent history as equally real; the formalism does not require that, and the record declines it. The fit reaches the record's strangest physics too. Its second decoherence channel, loud near a boundary and engineered to zero in a sealed cavern, is in this framework a term in the environment and not in the dynamics, and a Levril sculpting a probability gradient is shaping an environment, which standard quantum mechanics permits, never projecting an outcome, which it does not.

Two further fits are worth naming. The single-framework rule forbids combining statements from incompatible families, so a question meaningful in one may be unformulable in another; the scope ladder says the same of a fact past its scope, and the Cascade's Boundary Confusion rule says cross-Concordant readings can contradict and both be local-correct. And the interpretation's best-known weakness has an answer here. Fay Dowker and Adrian Kent showed in 1996 that nothing in the physics picks a preferred consistent family, so the everyday world goes unexplained. The Cascade's design strata fix possibility space and the admissibility windows drawn from it, the shape the branching takes, and leave which branch resolves to the present. The family is authored; the history is chance. The arrow of time has the same source in both: Gell-Mann and Hartle derive it from an initial condition with no final condition, and Hartle and Hawking's 1983 no-boundary proposal is a specification of that initial condition, which is what a Worldwright's authoring is, read from outside.

So the answer is a reading and not a change. Lore stays framework-neutral, since meaning comes from prediction, and a Codex source remains free to argue for consciousness and lose. What this entry claims is smaller and firmer: the record's own rules select one interpretation, and it is the one whose founders were trying to make sense of whole universes. Why that choice matters beyond taste, and what it has to do with a neighbouring archecluster whose quantum mechanics is not ours, is the second entry's subject.

References: R. B. Griffiths, "Consistent histories and the interpretation of quantum mechanics", Journal of Statistical Physics 36 (1984); M. Gell-Mann and J. B. Hartle, "Quantum mechanics in the light of quantum cosmology", in Complexity, Entropy and the Physics of Information (1990); J. B. Hartle and S. W. Hawking, "Wave function of the universe", Physical Review D 28 (1983); F. Dowker and A. Kent, "On the consistent histories approach to quantum mechanics", Journal of Statistical Physics 82 (1996).