Sentience is the capacity to experience anything – the fact that when your brain is thinking or processing visual information, you actually feel what it’s like to think and to see.
The following thought experiment demonstrates, step by step, why conscious experience must be a product of functional patterns, not any specific physical material or structure.
The Inevitable Self-Report of Sentience
Consider a person who says, ‘Wow, it feels so strange to see and to think,’ speaking of their own conscious experience.
Every human action results from precise patterns of neuronal firing, cascading through the brain until reaching motor neurons that cause them to take actions, in this case to produce speech describing their sentience. Brains are bound by the laws of physics – if the same neurons fire with the same timings, it will result in the same outward behavior with absolute certainty.
It cannot be perpetual coincidence that our subjective experience always lines up with what our brain and body are doing. There is some reason for the synchronization.
When someone talks about their sentience, the state of being sentient must influence their behavior – otherwise, it would be physically impossible for them to speak about their sentience. The mere fact that they can describe their experience means that sentience has played a causal role in their behavior.
Now, replace one neuron with a functionally identical unit, one that takes the same inputs and fires the same way. The behavior of the person remains the same, and they still say, “Wow, it feels so strange to see and to think.” This remains true if you replace more neurons – even the entire brain – with functionally equivalent units. The person will still say the same thing.
Taking it further – replace the entire brain with a single piece of hardware that takes in the same sensory input signals and produces the same outputs to the motor neurons, using software equivalents for each neuron. The person will still say, “Wow, it feels so strange to see and to think.”
Since discussing one’s sentience proves that sentience influences behavior, and we have ruled out anything other than firing patterns as capable of driving behavior, it follows that sentience emerges from these firing patterns and their functional relationships. Sentience doesn’t require biology, quantum magic, or any particular physical substrate beyond something capable of modeling these patterns. Sentience emerges from the patterns themselves, not from what creates them.
just read his post. interesting to see someone have the same train of thought starting out, but then choose different aspects to focus on.
Any non-local behaviour by the neurons shouldn't matter if the firing patterns are replicated. I think focusing on the complexity required by the replacement neurons is missing the bigger picture. Unless the contention is that the signals that arrive at the motor neurons have been drastically affected by some other processes, enough so that they overrule some long-held understanding of how neurons operate, they are minor details.
"The third assumption is one you don't talk about, which is that switching the substrate without affecting behavior is possible. This assumption does not hold for physical processes in general; if you change the substrate of a plank of wood that's thrown into a fire, you will get a different process. So the assumption is that computation in the brain is substrate-independent"
Well, this isn't the assumption, it's the conclusion (right or wrong). It appears from what I can tell is that the substrate is the firing patterns themselves.
I haven't delved too deeply into Penrose's stuff for quite some time. What I read before doesn't seem to explain how quantum effects are going to influence action potential propagation on a behaviour-altering scale. It seems like throwing a few teaspoons of water at a tidal wave to try to alter its course.