Lost Schrödinger Manuscript Upends His Reputation as a Champion of Determinism
A lost Schrödinger manuscript reveals a twist in quantum physics

A three-page manuscript by Erwin Schrödinger, hidden in an Austrian library for over 80 years, reveals his unpublished rebuttal to a 1943 argument against hidden variables. Physics historian Flavio Del Santo found that Schrödinger defended the possibility of determinism while personally embracing indeterminism—a stance he held even before quantum mechanics. The document challenges the common portrayal of Schrödinger as a defender of clockwork physics.
The strongest plea in favor of indeterminism is older than quantum mechanics.
- darkslide3000
It's funny that world-leading physicists were arguing about these questions in the 40s (even if briefly), because I feel like nowadays, everyone who has played Civilization would've intuitively known Whittaker's argument to be flawed (at least those of us that like to savescum). A photon with hidden variables is essentially like playing a game of Civilization with the "preserve random seed" option enabled: if you reload a save and then take the same action (e.g. order unit X to attack unit Y) 100 times, you'll get 100 times the same result (e.g. unit X wins) — just like a deterministic photon would always take the same path. But if you load that same save and then take a different action (e.g. first order unit A to attack unit B, and then order unit X to attack unit Y) you may get a different outcome (e.g. unit X might die), because the PRNG from that same random seed is fed operations in a different order. The result can still be absolutely deterministic, but nevertheless dependent on external inputs. Same for the photon that could start acting differently in a way that is still tied to its hidden variable state when the environment it is confronted with changes (as if each quantum particle was seeded with its own little PRNG).
Of course Bell later proved by experiment that quantum state cannot be explained as simply as a local hidden variable, no matter how it looks like. But these guys didn't know that yet.
- luc4
To give some nuance on the quote "Experimental evidence + logical deduction can never prove that either the deterministic or the indeterministic view is impossible": We can indeed rule out a local hidden variable model [1].
So if the deterministic view is true, then it has to be a holistic theory. The hidden variables must be global, i.e. "accessible" throughout the universe. They cannot be attached to a particle as in Whittaker's model or Schrödinger's modification.
- artnap
Schrödinger's fix to Whittaker's photon argument was to let the hidden variable take any value between zero and one, instead of just two. It's funny that such a small change was enough to rebuild the quantum probabilities.
- hackandthink
Robert W. Spekkens (and I guess Matt Leifer) tried to model quantum uncertainty classically.
(my gut feeling was: it works till it does not work)
"In defense of the epistemic view of quantum states: a toy theory"
- rolph
https://phaidra.univie.ac.at/api/object/o:167065/download [PDF]