Only Physics Computes

There are some famous “honeypot” topics that suck in many people, but where few make any progress. I usually avoid them. But I was recently pulled into discussing “consciousness”, and realized I do have something new to say about that. New to me that is; I can’t be bothered to read enough of the vast related literature to see how original this is.

The key assumption on which I want to build my analysis is: computation (really “signal processing”) only happens in our familiar physical universe. In particular, the state of our brains at any one time results from the familiar matter of our brains, i.e., photons, electrons, protons, and neutrons, interacting according to familiar physical laws to compute the future states of our brain.

A great many of us reasonably assume that we will eventually have a satisfactory account of how our brains compute our feelings. That is, how we come to report and remember having feelings, with different particular feelings at different times. We feel pretty sure that we will eventually have a solid robust story about how our brains figure out which feelings we are to have when as a result of our input signals and all that internal brain computation. A story wherein pretty much all of that computation happens within and between our usual brain cells. A story that fits well with our usual counterfactual claims re different input signals, internal architecture, or effects of our actions.

Now when we have such an account, we should be able to extend it to many similar physical systems, to be able to say what it would take for them to be able to compute feelings. At which point we would know for a wide class of physical systems exactly what feelings those systems would have, if they had any feelings whatsoever.

Now consider the “hard problem” sort of question of human “consciousness”, where one assumes that we could have exactly the same physical state paired with with no feeling or actual feeling. This question must come down to basically: which of the many physical systems that compute feelings, and so could potentially have such feelings, actually do have such feelings. Somehow the universe would have to have a rule or process by which it decides which of these computed potential feelings are realized as actual feelings.

Now let me invoke my key assumption: computing only happens in physics. If so, then this rule or process can’t be very complicated, as it would otherwise require substantial computation to figure out what that rule implies in any given case.

One simple rule is: all computed potential feelings are actual feelings. Note that this doesn’t imply that all electrons, or all spacetime volumes, feel. After all, the dimensionality of the space of human brain feelings is vastly smaller than is the dimensionality of the physical states of those brains. Or even then the dimensionality of the signal processing subspace of that system. Thus, if humans are a guide, only a tiny fraction of physical system dimensions typically correspond to independent “feelings”.

I can think of many other simple rules. Like that we feel when the strength of the nearby gravitational field, or matter temperature is the proper range. But these seem just silly and arbitrary to me as theories of how our universe works. And so I lean toward the simple rule: all computed potential feelings correspond to real feelings. The universe feels when it can.

Added 11p: If you think that the universe is picky about which computed feelings are allowed to actually feel, and if you value actually feeling over being an unfeeling zombie, then you should be very wary of changing anything about your life. After all, you at best only know that you now feel; you don’t actually know if you ever felt before or if anyone else has ever felt before. So any change of any physical parameter in your immediate environment risks turning you into a zombie.