Process Physicalism¶

The Four-Model Theory is physicalist: both substrate and simulation are physical processes, with consciousness constituted by the process of self-simulation rather than identical to any particular neural state.

Consciousness theories must take a stance on what consciousness is made of. Dualism posits non-physical substance. Panpsychism posits fundamental experiential properties. Identity theory equates consciousness with specific neural states. Functionalism identifies it with functional roles. The Four-Model Theory charts a different course: process physicalism, in which consciousness is constituted by a specific physical process -- ongoing self-simulation across four nested models operating at criticality.

What Makes It Physicalist¶

There is no non-physical substance in the theory. No fundamental experiential property. No panpsychist micro-experience. Both the substrate (the implicit models stored in synaptic weights and connectivity patterns) and the simulation (the explicit models generated as dynamic computational processes) are physical. Qualia are higher-order physical patterns -- specifically, patterns of activity within the simulation that constitute the ESM's self-perception within the EWM.

Everything the theory invokes is physical. What it adds is a level distinction: the substrate level and the computational level have different properties, but both are physical. A spreadsheet is physical -- it runs on physical hardware, consumes physical energy, and produces physically measurable outputs -- yet no transistor "contains a sum." The sum is a property of the computational level. Qualia work the same way.

What Makes It Process¶

The crucial word is process. Consciousness is not identical to any particular neural state (as type-identity theory would have it). It is constituted by the ongoing activity of self-simulation. The same conscious state could, in principle, be realized by different physical substrates -- what matters is the functional architecture (four models at criticality), not the specific material. This is why the theory entails substrate independence.

Process physicalism avoids two familiar difficulties. Type-identity theory struggles with multiple realization: if consciousness is a specific neural state, how can corvids with no neocortex be conscious? Traditional functionalism struggles with the Hard Problem: if consciousness is "just" a functional role, why does it feel like anything? The Four-Model Theory resolves both by adding the real/virtual split to standard functionalism. Qualia are not just functional roles but virtual properties of the simulation -- real as virtual properties, genuinely experiential but not properties of the substrate.

Positioning Among Rivals¶

The diagram below shows where process physicalism sits relative to other positions in the philosophy of mind.

Figure¶

graph TB
    PHYS["Physicalism"]
    DUAL["Dualism"]
    PAN["Panpsychism"]

    PHYS --> ID["Identity Theory<br/><i>Consciousness = neural state</i>"]
    PHYS --> FUNC["Functionalism<br/><i>Consciousness = functional role</i>"]
    PHYS --> PP["Process Physicalism<br/><i>Consciousness = self-simulation process</i>"]

    DUAL --> SD["Substance Dualism<br/><i>Non-physical mind</i>"]
    DUAL --> PD["Property Dualism<br/><i>Non-physical properties</i>"]

    PAN --> CPAN["Constitutive Panpsychism<br/><i>Micro-experiences combine</i>"]

    PP ---|"adds level distinction"| FUNC
    PP ---|"avoids"| CPAN

    style PP fill:#2d1b69,stroke:#9b59b6,color:#fff,stroke-width:3px
    style ID fill:#2c3e50,stroke:#34495e,color:#bbb
    style FUNC fill:#2c3e50,stroke:#34495e,color:#bbb
    style SD fill:#2c3e50,stroke:#34495e,color:#bbb
    style PD fill:#2c3e50,stroke:#34495e,color:#bbb
    style CPAN fill:#2c3e50,stroke:#34495e,color:#bbb
    style PHYS fill:#1a1a2e,stroke:#333,color:#aaa
    style DUAL fill:#1a1a2e,stroke:#333,color:#aaa
    style PAN fill:#1a1a2e,stroke:#333,color:#aaa

Process physicalism (highlighted) extends functionalism by adding a level distinction -- the real/virtual split -- that allows it to address phenomenality. Unlike identity theory, it permits multiple realization. Unlike panpsychism, it requires no micro-experiences and faces no Combination Problem.

Key Takeaway¶

Process physicalism holds that consciousness is constituted by a physical process -- self-simulation -- not identical to any neural state, not a functional role alone, and not dependent on non-physical substance. The real/virtual level distinction is what separates it from traditional functionalism and allows it to address the Hard Problem.