It's odd, I know, but entirely factual. All sensation, all your experience of anything ever is a processing output of your brain.
Certainly if you hit my hand with a sledgehammer i will scream about my hand hurting. But what has happened? Nerves depolarise, synapses communicate, a pattern of activity emerges in my brain. And as the conscious entity experiencing that pattern, i experience pain.
If my spinal cord is severed (and i survive otherwise intact) those signals never reach my brain, and i experience no pain. No physical pain as a direct result of your actions, anyway. I may still be annoyed :)
Your experience is 100% dependant on and exclusive to your brain, sledgehammer or no.
Yes, your subjective experience has its locus in your brain, but that is not at all the same thing as "Everything you will ever experience is all in your head." There is an external reality that is separate from your brain. Some of the things you experience (like getting hit on the head with a sledgehammer) involve processes that operate in this external reality, and others (like dreams or psychosomatic pain) don't. This is a salient and useful distinction which "Everything you will ever experience is all in your head" only serves to obscure.
Okay so this may feel like splitting hairs, but...
You're talking about input, I'm talking about output.
Experience is influenced (to varying extent) on sensory input, but they're not the same thing.
Sensory input of course influences experience, I'm not going to deny a sledgehammer to the hand.
While you feel that the distinctions drawn above serve only to obscure things, in fact the reverse may be true. The Cartesian perspective that "output is nothing but a response to input" has been pretty much discarded in modern research into pain, neurology, consciousness, psychiatry, and so on.
So i don't deny the role of sensory input. I'm just pointing out that input is distinct from output; they're not the same thing.
> I'm just pointing out that input is distinct from output; they're not the same thing.
That's obviously true, but that's a very different statement than the one you originally made, namely, "Everything you will ever experience is all in your head."
In response to your new statement I will say: I understand what "input" means, but I can't imagine what "output" could possibly mean in the context of a discussion on subjective experience.
If you mean that whatever combination of neurons fire to produce a subjective experience in response to external stimuli can also be triggered without those external stimuli in some cases, then yes, that is also obviously true. But that is also a very different claim than "Everything you will ever experience is all in your head."
I feel we may both be pushing on the same open door.
>> I'm just pointing out that input is distinct from output; they're not the same thing.
> That's obviously true, but that's a very different statement than the one you originally made, namely, "Everything you will ever experience is all in your head."
Nope, it's exactly the same. Experience is output, and entirely in your head. Sledgehammers to the body are input. Everything you will ever experience is entirely output. Sledgehammers will influence that output, but input and output are not the same. They are tightly coupled, and one of course strongly influences the other.
I agree with you that these are salient and important distinctions. I simply disagreed with your assertion that "It (experience) is not all in your head." It really is. After all, where else would your experience be?
Okay enough splitting hairs. Personally I feel the distinction is clear and highly relevant. Some references I should have provided earlier:
There is no clear line which makes a sensation external or internally based. It's a messy abstraction, but there's some meaning behind it, because things can at least be relatively sorted by how external or internally based they are. For example, you may see a spider which 99.99% of sighted individuals would also see and agree there was a spider there, or you can hallucinate one, where only you would agree about a spider being present. Clearly the first is MORE externally based than the latter.
Certainly if you hit my hand with a sledgehammer i will scream about my hand hurting. But what has happened? Nerves depolarise, synapses communicate, a pattern of activity emerges in my brain. And as the conscious entity experiencing that pattern, i experience pain.
If my spinal cord is severed (and i survive otherwise intact) those signals never reach my brain, and i experience no pain. No physical pain as a direct result of your actions, anyway. I may still be annoyed :)
Your experience is 100% dependant on and exclusive to your brain, sledgehammer or no.