Markus Reiher's April 2026 arXiv preprint (not yet peer-reviewed) offers a perspective piece rather than new empirical results or formal theorems. Drawing on mathematical physics and his group's expertise in computational molecular science, Reiher argues that quantum mechanics' century-long reliance on Hilbert-space formalisms creates a mismatch with real-world computing done in finite dimensions and with finite numerical accuracy. No datasets, simulations, or sample sizes apply here; instead, the work synthesizes concepts from prolate spheroidal wave functions, short-time quantum dynamics, and spectral theory to advocate a foundational reset.

The proposal is radical yet pragmatic: treat measured signals as the primary reality. Wave functions and Hamiltonians become auxiliary constructs we build afterward to rationalize patterns in those signals. A key technical insight is a 'signal-based spectral equation' that turns frequency analysis into an operator problem. This reveals a sharp accuracy transition—below a critical observation time tied to a signal's effective spectral density, resolution collapses; above it, accurate reconstruction becomes possible. The preprint links this to existing results on prolate Fourier theory and effective quantum simulation but stops short of full philosophical synthesis.

This is where the work addresses gaps that have frustrated philosophy of science since the 1927 Solvay Conference. Einstein and Bohr's debate over whether the wave function describes reality or merely our knowledge has splintered into dozens of interpretations (Copenhagen, many-worlds, objective collapse, relational QM) with little mainstream uptake in day-to-day physics. Coverage of quantum foundations usually misses the computational chemists' perspective that Reiher foregrounds: even 'exact' diagonalizations are effective approximations once systems exceed a few dozen atoms. By centering finite observation windows from the start, the framework integrates approximation not as an engineering inconvenience but as a foundational necessity.

Synthesizing this preprint with two earlier strands illuminates connections others overlook. David Slepian and Henry Pollak's landmark 1961 papers on prolate spheroidal wave functions (Bell System Technical Journal) already demonstrated the remarkable concentration properties that Reiher invokes; they showed that signals observed over finite time occupy an effectively finite-dimensional space, a fact under-used in quantum foundations. Pairing this with Christopher Fuchs' QBism framework (see 'QBism, the Perimeter of Quantum Bayesianism,' arXiv:1003.4555) creates a deeper resonance: both treat measurement outcomes as primitive and quantum states as tools for updating expectations. Add Wojciech Zurek's decoherence program, and a coherent picture emerges—effective degrees of freedom and classical-like signals arise naturally once we accept resource-bounded observers embedded in complex quantum systems.

What the preprint under-emphasizes is how thoroughly this observation-centered stance challenges realist interpretations that insist the wave function is a literal, universal entity evolving unitarily forever. It also opens practical doors the philosophy literature rarely touches: better effective models for molecular electronic structure, where identifying the 'right' active degrees of freedom has always been more art than algorithm. Limitations remain—the proposal is programmatic, not yet a complete mathematical theory, and its claimed 'sharp accuracy transition' needs wider testing across physical domains.

A century after Heisenberg and Schrödinger, Reiher's constructive program suggests quantum mechanics may mature not by resolving what 'really' happens between measurements, but by accepting that all descriptions are effective, observationally grounded, and computationally bounded. This pragmatic synthesis could finally move foundational debates from perpetual philosophy seminars into the daily practice of simulation and discovery.