Reactive Substrate Theory and Jacob Barandes on Quantum Foundations

In a recent conversation hosted on Theories of Everything, Harvard physicist and philosopher Jacob Barandes and MIT’s Manolis Kellis discuss what they see as deep problems with the last hundred years of quantum theory, especially around ontology, superposition, and the status of the wavefunction. Their critique aligns remarkably well with the motivations behind Reactive Substrate Theory (RST), even though they stop short of proposing a concrete medium-based model. This post summarizes the overlap and the differences, and shows how RST can be seen as one possible realization of the kind of theory they say is missing.

Barandes’s Main Claims in Brief

Barandes’s professional focus is the intersection of philosophy and physics, with an emphasis on the foundations of quantum mechanics, classical and quantum field theory, and the metaphysics of causation and probability. In the interview, he and Kellis highlight several key points about quantum theory:

Superposition is often misrepresented: Saying “a particle is literally in two places at once” is, in his view, a misleading way to describe the formalism.
Quantum mechanics is formally powerful but ontologically silent: The theory tells us how to compute probabilities, not what the world is made of between measurements.
Wavefunctions are not straightforwardly “real” fields in 3D space: They live in configuration space and are not obvious physical beables.
Fields (like the electromagnetic field) are far better candidates for reality than particles: He leans toward field realism over particle ontology.
Copenhagen is incomplete and many-worlds is ontologically extravagant: Both are criticized as unsatisfactory attempts to interpret the same formalism.
Quantum theory may be a powerful calculational tool, not the final description of reality: He suggests we still lack a deeper, physically transparent theory.

These themes—dissatisfaction with Copenhagen, skepticism about literal superposition, realism about fields, and the call for a deeper, ontological theory—are exactly the issues that RST sets out to address.

Reactive Substrate Theory: The Missing Ontology

Reactive Substrate Theory starts from a simple ontological claim: there is a real, continuous, nonlinear, bandwidth-limited medium filling space, called the Substrate. All the phenomena we call “quantum,” “electromagnetic,” and even “gravitational” are manifestations of wave dynamics in this medium. The central dynamical equation is:

(∂t²S − c²∇²S + βS³) = σ(x,t)⋅FR(C[Ψ])

Here S is the Substrate field, ∂t²S and ∇²S describe wave propagation, βS³ encodes nonlinear self-interaction, and the right-hand side represents the way matter configurations Ψ compress and drive the medium via a bandwidth-limited reaction FR. This is a fully ontological, field-based picture, in exactly the sense Barandes argues is missing from standard quantum mechanics.

Does RST Agree, Disagree, or Add to Barandes’s Views?

1. On Superposition and “Particles in Two Places at Once”

Barandes criticizes the popular claim that quantum particles are literally in two places at once, arguing that this is a misinterpretation of the formalism. RST agrees. In RST, there are no point particles “splitting” across space. There is a single continuous Substrate field S(x,t), and what we call “superposition” is just the coexistence of multiple wave modes in one medium. Measurements probe that medium with finite bandwidth and resolution; they do not reveal a particle hopping between branches.

2. On the Incompleteness of Quantum Mechanics

Barandes emphasizes that quantum mechanics is silent about what happens between measurements and does not provide a clear ontology. RST explicitly disagrees with this agnosticism: it asserts that there is a real medium, governed by a concrete partial differential equation, evolving continuously whether or not anyone measures it. Where Barandes calls for a deeper, physically transparent theory, RST proposes one: the Substrate and its dynamics.

3. On the Status of the Wavefunction

Barandes is skeptical of treating the wavefunction as a literal physical field in 3D space, since it lives in configuration space. RST sidesteps this issue by demoting the wavefunction to an informational construct: ψ encodes knowledge or statistical structure, not the direct physical state. The physically real entity is S(x,t), a field in ordinary space, with ψ emerging as an effective description of certain coarse-grained behaviors of that field.

4. On Field Realism

Barandes is much more sympathetic to the idea that fields—like the electromagnetic field—are real beables than to the idea that particles or wavefunctions are fundamental. RST strongly agrees and goes further: all the familiar fields are treated as different modes or effective regimes of the single underlying Substrate. This unifies field realism into a single medium-based ontology.

5. On Interpretations: Copenhagen and Many-Worlds

Barandes is critical of Copenhagen-style anti-realism and also of many-worlds’ ontological excess, seeing both as unsatisfactory attempts to patch an incomplete formalism. RST concurs. In RST there is no fundamental wavefunction collapse and no branching universes. There is one world, one medium, and one evolving field S, with measurement outcomes arising from the way a bandwidth-limited Substrate reacts to localized couplings σ(x,t).

6. On Quantum Theory as a Computational Shortcut

The video explores the idea that quantum theory might be more of a highly efficient computational scheme than a literal description of the underlying processes. RST partially agrees: it treats standard quantum mechanics as a statistical, emergent description of Substrate dynamics, not as the foundational level. Where it diverges is in replacing computational metaphors with a concrete mechanical medium: the apparent “computation” is just the time evolution of S under the RST equation.

Comparison: Barandes vs. RST

The table below summarizes key points of agreement and difference between Jacob Barandes’s expressed views in the interview and the RST framework.

Topic	Barandes (as presented in the interview)	Reactive Substrate Theory (RST)
Superposition	Rejects the slogan “particle in two places at once” as misleading; superposition is a feature of the formalism, not literal splitting.	Agrees; superposition is multiple wave modes in a single Substrate. No literal particle duplication.
Ontology Between Measurements	Standard QM is silent on what “really happens” between measurements and may be incomplete.	Provides a concrete ontology: a real Substrate field S(x,t) evolving continuously via the RST equation.
Status of the Wavefunction	Wavefunction is not obviously a real field in 3D space; lives in configuration space.	Wavefunction is informational; the physically real entity is S(x,t) in ordinary space.
Fields vs Particles	More sympathetic to fields as beables; particles are less fundamental.	Fully field-based: all “particles” are excitations or localized reactions of the Substrate.
Copenhagen Interpretation	Viewed as philosophically unsatisfying and incomplete.	Explicitly rejected; RST insists on a real, continuous medium and dynamics.
Many-Worlds Interpretation	Seen as ontologically heavy and problematic.	Rejected; RST is a single-world theory with one evolving medium.
Role of Quantum Theory	May be a powerful calculational tool rather than a literal description of reality.	Agrees; QM is emergent. The fundamental level is Substrate dynamics, with QM as an effective theory.

RST as a Concrete Realization of the “Missing Theory”

One of the most striking aspects of the Barandes–Kellis conversation is the repeated claim that our current quantum formalism lacks an underlying, physically intelligible model of what is really happening in the world. They outline desiderata: continuity, causality, field realism, and a clear ontology that recovers quantum predictions as an emergent layer. RST is designed to meet exactly those requirements, by positing a universal reactive medium with a well-defined dynamical equation.

In this sense, RST does not oppose the concerns raised in the interview; it answers them. Wherever Barandes says “quantum theory doesn’t tell us what’s going on,” RST says “here is one possible picture: a nonlinear Substrate field, evolving under a specific PDE, from which the familiar quantum phenomena emerge as statistical behavior.”

Conclusion

The interview with Jacob Barandes and Manolis Kellis is less a defense of quantum orthodoxy and more a critique of its conceptual incompleteness. Reactive Substrate Theory stands very close to that critique in spirit, but goes a step further by offering an explicit medium-based ontology and a concrete dynamical law. Where the video argues that quantum theory by itself is not enough, RST proposes a deeper layer of description that can, in principle, be tested, modeled, and used to derive the quantum formalism as an emergent approximation.

Whether RST is ultimately correct is an empirical question. But it squarely addresses the philosophical and physical worries that Barandes raises—and that alone makes it a worthwhile candidate for the kind of “next theory” he suggests we still need.

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