Sean M. Carroll (2021), arXiv preprint (invited contribution to Quantum Mechanics and Fundamentality, ed. Valia Allori) — ARXIV-2103.09780
Key takeaways
- Carroll argues that the complete fundamental ontology can be a unitarily evolving vector in Hilbert space plus the Hamiltonian’s energy spectrum, with subsystems, classicality, space and fields recovered as emergent, non-generic structure via “quantum mereology”.
Seeded from the abstract and a skim, before the reading in NOTE-134. What follows is what the work says about itself.
Carroll defends the self-described extreme view (“Mad-Dog Everettianism” / Hilbert space fundamentalism) that the world is fundamentally just a vector in Hilbert space obeying the Schrödinger equation. On this view the laws of physics are fixed entirely by the energy eigenvalues of the Hamiltonian. Everything recognisable — space, and the fields in it — is to be recovered as a higher-level emergent description. He sketches a route to that recovery while conceding much remains to be done.
Standing in the record
Filed from the 2026-09-26 sweep of the papers-feed tracker for philosophy: 10 seconds of active reading over 2 sessions. It was filed Deferred, unread. NOTE-134 is the close reading of 2026-09-26, and it placed the work: Active — worth reading as the shortest authoritative statement of Hilbert-space fundamentalism and its “quantum mereology” programme, with the caution that nothing is derived in it. Every technical claim is delegated to a companion paper, and the author says the programme “may ultimately fail” (p. 12).
When seeded, before the reading in NOTE-134, the entry gave a priority for a deeper reading: medium — low reading time (t = 10 s) but a central, short statement of a live position; the skim covers the programme, while its load-bearing technical claims live in cited companion papers.
What the seeding asked a deeper reading to check (NOTE-134 is that reading):
- A clear statement of an extreme structuralist/emergentist ontology; pairs naturally with Rovelli’s relational view (LIT-177) as opposite poles on the reality of ψ.
- Check the uniqueness claims for the quasi-classical factorisation (Carroll & Singh 2019) against the known “preferred factorisation” objections (e.g. Stoica’s arguments that spectrum-only structure underdetermines physics).
- Check whether “equally real” emergent structure amounts to a substantive metaphysics of emergence or a pragmatic one.
Access when seeded: arXiv abs page (v1 submitted 17 Mar 2021, report no. CALT-TH-2021-010) and full PDF (16 pp.) read directly; sections are unnumbered, so locations are PDF pages. The DOI of the eventual book chapter was not checked.