# A Falsifiable Causal Argument for Substrate Independence

Here's a deceptively simple argument that derives an empirically falsifiable conclusion from two uncontroversial premises. No logical leaps. No unwarranted philosophical assumptions. Just premises, deduction, and a clear way to falsify.

I'll present the argument first, then defend each piece in turn. The full formal treatment is in the paper linked at the end.

*   Premise 1 - *The Principle of Causal Efficacy (PCE)*: Conscious experience can exert some causal influence on behavior. 
*   Premise 2 - *The Principle of Neural Mediation (PNM)*: All causal paths from brain to behavior eventually pass through which neurons spike when. 
*   Conclusion: The temporal pattern of neuron spikes is sufficient for manifest consciousness.

By “manifest consciousness,” I mean those aspects of experience that can, in principle, make a difference to behavior, including self-report. Non-manifest aspects of consciousness are empirically unreachable, and their existence doesn't undermine the manifest case.

To avoid this conclusion, one must either reject Premise 1 (epiphenomenalism, handled below), or reject Premise 2, which can be falsified by demonstrating a way to alter intentional behavior without altering spike patterns.

*Note: this argument relies heavily on self-reports. Assume the reports come from reasonably lucid, unimpaired, earnest subjects. The logic doesn’t require all subjects to fit that description, only that such subjects can exist in principle.*

Defending Premise 1: The Principle of Causal Efficacy (PCE)
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### *"Conscious experience can exert some causal influence on behavior. "*

We treat self-reports as translations of experience. This is the gold standard across multiple scientific fields:

*   *"Does your leg hurt? How about after taking this pill?" *
*   *"Do you feel fully awake right now?" *
*   *"Do you still feel depressed on this medication?"*

Even when we develop objective measures (e.g. EEG, fMRI), the subject's report is treated as ground truth. If a bright-eyed subject reports feeling awake and alert, while the machine says they're unconscious, we question the machine or the theory, not whether the person is actually conscious. For our purposes, we don't need self-reports to be perfectly accurate; we just need them reliable enough that entire scientific fields can be built on the data they provide.

We also do this in daily life: 

*   *"Are you feeling any better today?" *
*   *"Isn't this beautiful?" *
*   *"I was so scared." "Yeah, me too." *

When we communicate about felt states, we act as if the communication reflects the inner state better than random noise.

### **Eliminating Epiphenomenalism: **

There is no consciousness detector to prove the flow of causation from experience to behaviour, so we must use evidence and causal/interventionist logic to make epiphenomenalism epistemically untenable.

First, we must establish experience as being somewhere in the causal chain. Our behaviour - specifically self-report - can function as a reliable translation of our experience (within the limits of language). Without both experience and behaviour sharing the same causal graph, that universal covariation would be just perpetual inexplicable coincidence, i.e. unscientific.

We'll keep this simple (formal treatment in Section 3 of the paper), but I think it's more legible to give ourselves a few symbols to work with: 

*   **E : the content of experience (what it feels like to see red, or be happy, or to think about things) **
*   **U : the behaviour (utterance) about one's experience **
*   **Z : a hypothetical common cause to both of them**

This leaves us with only two reasonable options. Either:

*   experience at least partially causes behaviour (**E** causes **U**), or
*   there is a common cause that causes both experience and behaviour (**Z** causes both **E** and **U**).

Our premise 1 is that **E** causes **U**, so we will focus on the common cause hypothesis: 

First let us define one last symbol (I promise): 

*   **K : a reporting policy.**

This reporting policy might be a very coarse: 

*   *"Only tell me whether you're conscious or not" *

Or a more detailed: 

*   *"Tell me the color you see in front of you, the emotion you're feeling right now, whether you're comfortable, and anything else you can think of that you're currently experiencing" *

Or it can even be a convoluted: 

*   *"When you see a fruit on the screen, take the 3rd letter of the name of the fruit, and figure out a color that starts with that letter, and tell me how you feel when you picture that color in your mind"*

The fact that **U** is reliably a translation of **E** through any reporting policy **K** starts to make the common cause view a little shaky. If **E** is causally idle, then it should function like an exhaust fume/side effect of common cause **Z**, while the main purpose is to drive behaviour. The fact we can perform any intervention **K** and have **U** maintain the correct mapping to **E** is difficult to reconcile for a common cause framework.

The only reasonable move from there is to invoke a common cause **Z** rich enough to fully map experience to behavior over any **K**. However, also contained in **E** is the felt sense of translating experience into report; the experiential "what-it's-like-ness" of that translation process and its success. This means that Z must also contain it in order to feed it to both **E** and **U**.

This sort of "intentional" illusion is difficult to justify through any evolutionary argument where **E** can have no effect on behaviour. Set that aside, and we're still left with a **Z** that has enough information to fully define the shape and character of **E**, as well as the translation step from **E** to **U**. this leaves the epiphenomenalist one of two moves: 

*   A: Accept that **Z** fully defines the shape and character of **E**. Any epiphenomenalists who accept physics and basic neuroscience accept that **Z** must be implemented in the brain. Therefore if PNM (Premise 2) holds, **Z** has everything needed to fully define **E**, **Z**'s only route is through spikes, and thus they agree with our spike pattern sufficiency conclusion, albeit through a needlessly circuitous route. 
*   B: Be left with a situation where **Z** contains enough information to fully define **E**, but that information is not used in shaping the manifestation of **E**. This is explanatorily indefensible: 
    *   Why would **Z**'s representation of experience perfectly mirror the actual shape of experience, with no causal link explaining the correspondence? 
    *   And if **Z** is already feeding causally into **E**, why would that information not have been used in the mirroring?

Option **A** accepts our conclusion. 

Option **B** is an inexplicable perpetual coincidence.

Defending Premise 2: *The Principle of Neural Mediation (PNM)*
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### *"All causal paths from brain to behavior eventually pass through which neurons spike when. " *

Sherrington's "final common path" has been battle-tested as motor neuroscience 101 for over a century. It states that all movement (behaviour) must ultimately pass through lower motor neurons. It is treated as essentially *fact* among neuroscientists. No reproducible example has ever been documented of a behavior-changing manipulation that leaves the relevant spike pattern intact. PNM remains unfalsified.

Defending and Elaborating On the Deduction: 
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*"The temporal pattern of neuron spikes is sufficient for manifest consciousness." *
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With PCE we have established that consciousness can have some causal influence on behaviour, and with PNM, that the path to behaviour always eventually passes through neuron spike patterns. The only remaining move is to eliminate anything upstream of neuron spikes from being necessary for conscious experience. We won't need to go into detail about each, but for the neuroscience people, we're referring to glia, ephaptic fields, hypothesized quantum microtubules, etc, that have any ability (hypothetical or otherwise) through any route to eventually help resolve whether a neuron spikes or not.

The way we eliminate these is by screening them off causally. Spikes occupy a unique place in the brain as causal influences to behaviour for a few reasons. They are the only mechanism that contains (all in one package) the specificity, speed, long-range transmission, and density to encode complex stimuli in the way we experience and express it. But more importantly, every other factor eventually resolves to either a neuron spiking, or not spiking. If it has no causal effect on a neuron spike (or non-spike), then it is behaviorally idle, violating PCE. If it does affect spikes, then it's causally degenerate - multiple configurations of upstream factors can produce the same spike outcome. This means that upstream factors have no mechanism to distinguish their contribution through behaviour. Multiple paths lead to any given spiking outcome, but if consciousness cared which route you took, it would have no way to tell you (violating PCE).

**Therefore, everything required for consciousness is encoded in neuron spiking patterns.** To falsify this, show *any* manipulation that alters intentional behavior without altering spike patterns.

Substrate Independence: 
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Interestingly, "neuron spiking patterns" can be defined very loosely; enough to establish substrate independence. If you replace any given one or more neurons (up to the entire brain) with any replacement, natural or artificial, and that replacement has the same downstream effects for any given set of upstream inputs, then you will replicate behaviour, including self-reporting behaviour where consciousness (per PCE) was part of the causal chain. This also holds for what I call "strong substrate independence", though I'm aware it's been called by other names. Essentially, the replacement "neuron" or node need not be a discrete physical object at all. If two or more functionally equivalent neurons (up to the entire brain) were implemented in software, and run on hardware that was connected to the same inputs and outputs, the same exact consciousness-dependent behaviour would result.

The full formal treatment is in the paper: [https://zenodo.org/records/17851367](https://zenodo.org/records/17851367)