No-New-Physics Consciousness - by Robin Hanson

Overcoming Bias

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No-New-Physics Consciousness

Robin Hanson<br>Aug 15, 2026

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There is a vast literature near the topic of this post, much of which has developed specialized vocabularies and concepts. And I can’t be bothered to master enough of it to make this post match it well. So please try to treat my words here as if their meanings came from other less specialized literatures.<br>Consider three kinds of systems:<br>Experience - Seen from the inside, a mind is aware of, can reason about, and might even “feel” a structure of experiences across time. These experiences are differentiated in many ways, and have many relations to each other.

Brain - In brains, signals pass from nodes to nodes, and each node collects input signals, transform those according to patterns, changes its internal state, and then sends signals out. Such sending and transforming takes time, and happens with error. At the edge, “sensor” interactions cause input signals and output signals cause “actuator” interactions.

Physics - Physical stuff, located in various space(time) alternatives, and of different types, is governed by simple self- and other- interaction rules re what happens when stuff is at the same place. These rules make stuff move and change. The transitive closure over interaction of stuff is a physical world.

A standard reduction view, which is also my view, is that each experience system is *made of some part (perhaps all) of a particular brain system, which is then made of a some part of a physical world system. When system A is “made of” system B, then A descriptions drop detail from and abstract from details of B systems, but add almost nothing that isn’t implicit in B. A complete description of B could in principle be used to calculate an almost complete description of A. (Some “almost” exceptions are discussed below.)<br>A standard physics view, which is also my view, is that we understand the physics near and in ordinary brains very well, and that such physics is pretty “complete”, with little room or need for new physics. This seems to imply the reduction view, in that if we found patterns or structures (POS) in experiences that couldn’t be accounted for by POS of brains, or POS of brains that couldn’t be accounted for by POS of brain material physics, then we’d have shown that our physics is incomplete, and in need of substantial revision.<br>I know of two claimed exceptions, of system features said to be unaccounted for in this system reduction to a complete physics view. The first claimed exception is that some physical worlds are “actual” while others are just “possible”. There is nothing inside a world that can tell you if it is actual or possible, and so actual vs possible is an additional fact about a world. The universe has some way that it determines which world(s) are actual, and not knowing this way makes our physics incomplete. Some have explored adding “boundary condition” rules to our usual physics interaction rules, but it isn’t clear to me if these are enough to set which world(s) are actual.<br>Note that one might want to allow some parts of the same physical world to be actual, while others parts were only possible. But this would require that possible stuff be able to interact with and influence actual stuff. To most, including me, this seems incoherent; only actual stuff can influence other actual stuff.<br>The second claimed exception is that some experience systems are said to “actually” feel their experiences, while other similar systems, with similar POS, and made of brains with similar POS, do not actually feel, but are instead “zombies” that only mimic real feelings. That is, it seems to many, including me, that it is often possible to create mimic brains that induce talk and actions similar to those in brains with associated experiences that really do feel, but where that appearance would be an illusion. Under a popular full-counterfactual view, that I also hold, we can go further to imagine a zombie alternative to any experience system that actually feels, with exactly the same other aspects of its experience, besides if it does or doesn’t really feel.<br>So there is a fact of the matter re if a particular experience system, and its supporting brain and physics systems, actually feels, or only appears to feel. Which makes it another exception to the physics view above. But unlike the actual vs possible physical world distinction, this distinction between actually and only apparently feeling experience systems can vary within parts of a physical world. Some brains in a world could have actual feelings, while other brains did not. Maybe even different parts of the same brain.<br>Note that under the physics view, there is no room for further unspecified aspects of experience systems. If an experience system feels, the details of its feelings are entirely set by the details of its brain. There is only a question of if such a system...