You have to Google and read those thought experiments to see why. You may not be convinced (I'm not), but they give good reasons. We have mechanistic explanations for all of those organs, and even if we lack some explanation, we know one is possible in principle. They argue this isn't the case for consciousness.
Philosophical zombies react to external events in exactly the same way as normal people, including internally, but we are told they lack conscious experience. Thus the thought experiment is set up from the start to find that conscious experience is something non-physical - or else the p-zombies don't really do what they're claimed to do, which is to react identically to everyone else.
There's a dubious implication that conscious experience is completely cryptic, with no effect on the outside world (such as a person speaking the words "I consciously experienced that"), or at least that all such effects are shallow enough that they can be perfectly faked. If this is true, we ought to question why it's such a big deal. What's so great about consciousness? Why associate it with rights?
The Knowledge Argument is about a scientist who learns "everything" about colors intellectually but doesn't see them until years later, and seeing a red tomato is a revelatory experience even after all that book-learning, so it implies that experiences are beyond knowledge, or beyond physics, or beyond tomatoes or something. But really all it shows is that intellectual learning is dry and dusty and limited. Like with the p-zombies, the premise is wrong. The scientist didn't really learn everything before having the experience, but could have done in principle but for the limits of communication, description, and simulation as we know those things presently. (And then the real experience would not have had any surprising or revelatory quale about it.)
> or at least that all such effects are shallow enough that they can be perfectly faked
Physicalism implies that things we wouldn't intuitively think of as conscious can perfectly mimic all such effects.
Imagine there's a person, John, and you take a precise scan of every neuron of his brain (or every particle if you prefer). You also record all the sensory input signals from his neurons to his brain. You write all this information down in a giant stack of papers. Then you go about simulating the brain with pencil and paper, computing its thoughts and actions (in this thought experiment people have deciphered exactly how neurons work). Maybe it takes you a trillion years to simulate one day of John's life, but you diligently do it.
Physicalism tells us that you can simulate John perfectly this way. You could perfectly predict every word is said, and every muscle he moved. You could feed the motor neuron outputs of your simulation into a robot replica of John, and it would act indistinguishably from the original John.
Is this pencil and paper simulation of John a p-zombie?
We either have to accept that this pencil and paper simulation of John is conscious, or that it's a p-zombie.
That's the normal physicalist position as far as I'm aware. Is there a physicalist theory where the simulation isn't conscious?
I was replying to a commenter who doubted that a non-conscious entity could mimic a person accurately. I'm pointing out the implication that without p-zombies, just by writing a bunch of stuff on paper, you created a conscious being. I'm not arguing that's false; just that intuitively it's a tough pill to swallow and if you don't want to accept that, p-zombies are the alternative.
> Thus the thought experiment is set up from the start to find that conscious experience is something non-physical
The point is that if you accept that p-zombies are possible, then you accept that consciousness is not necessarily physical. If it's not necessarily physical, then physicalism is false.
> really all it shows is that intellectual learning is dry and dusty and limited.
What it's attempting to show is the limit of factual knowledge. If physicalism is true, then everything that can be observed must reduce to objective third person facts. But, Mary has all of the objective third person facts. So if you find it implausible that Mary would be able to infer the experience of red before actually observing a rose, even with all of those facts, then you're admitting the existence of first person subjective facts, which cannot be reduced to objective third person facts, not even in theory.
Daniel Dennett has some great responses to these challenges.
Much though I'd be interested in Daniel Dennett's responses, I don't think you understood mine. I'm saying:
Mary doesn't have all of the objective third person facts, only the ones that can be conveyed to her academically.
If you want to sweep this aside with a magic gesture, and assert that she does somehow have all the facts (alright, all the objective third person facts), you are also making the science, communication, imaginative simulation, verbal learning process, all that kind of stuff, into something magical. Because what you're saying is that it now somehow has the power to be exactly like the real experience, which in this magical scenario will thus come as no revelatory surprise to her. We only expect it to be a surprise because of realism about the limits of book-learning as we know it, because she can only learn all that is explicitly known about colors that way, which is not all there is to know about them, and is not even all that is commonly known.
But like the brain, language is Turing-complete. Any information Mary's brain can figure out can also be described in language. If the brain could deduce something that couldn't be described with math and language, it would be doing something outside of our current understanding of physics.
You could respond that even though computability theory tell us it's possible to describe in language, the description would be far too long and complicated for Mary to understand. But I think that misses the thrust of the thought experiment. Even if we imagine Mary being so smart that she could understand and absorb the full written description of the color red, it still doesn't seem like that should be the same as experiencing seeing red. Most people's intuition would be that internal experiences are categorically different than facts.
And also, intuitively, the experience of the color red doesn't seem complex. The dumbest person on Earth can easily experience it, as can a newborn baby with no knowledge to draw on (I guess assuming newborns are sentient). Even a honey bee may be able to experience it. It's such a simple thing that it seems weird to think it's theoretically possible to describe with language, but the description is too complex for humans to understand.
It fundamentally feels weird to think that any combinations of words could ever be the same as experiencing the color.
> Mary doesn't have all of the objective third person facts, only the ones that can be conveyed to her academically.
The premise of the argument is that Mary has all of the facts, and you can even imagine that she has a super powerful computer accessible to her to perform any calculations needed. The goal is to point out that it still seems implausible that Mary could infer knowledge of the experience of redness despite having an unbounded set of dry facts about physics and biology, because to most people, qualitative experience seems like knowledge of a different kind.
That said, you're sort of on the path towards Dennett's response.
I think OP is saying that p-zombies are a pointless thought experiment, because the intended outcome is hardcoded in the premise. If you accept the premise, you ipso facto already believe that consciousness is not necessarily physical, and the experiment doesn't change that. If you reject the premise, then the experiment is nonsensical.
> I think OP is saying that p-zombies are a pointless thought experiment, because the intended outcome is hardcoded in the premise
Yes and no. The point is to actually test your intuitions around the premise and the conclusion that must follow, to clarify your own thinking around the intuitive plausibility of the conclusions and premises, hence why these are called intuition pumps. They don't prove anything definitively unless you have intuitions around consciousness that agree/disagree with the premises, but you don't necessarily fully understand your own intuitions until you think about this problem.
>If physicalism is true, then everything that can be observed must reduce to objective third person facts.
You are erroneously equating "physicalism" with "reductive physicalism". It's clear to many of us that qualia are something subjective and non-physical yet emerge from physical processes.
Yes, people are capable of convincing themselves of all kinds of nonsense. The kind of ontological emergence you would require in such a model of qualia is still of a completely different kind than any other kind of emergence, and so still requires extending the ontology of basic physicalism. There seems to be very little motivation to do so at this point. Let's not repeat the mistakes of vitalism.
The brain evolved to be intelligent. Intelligence is the ability to model the outside world in order to make predictions and then choose an optimal course of action. More intelligent beings are generally more "fit" in the evolutionary sense. Hence how humans have conquered all the ecosystems on the planet.
Turns out, consciousness/experience/qualia is an unexpected side effect of this process. We can "feel" the intelligence happening.
Where we humans get lost is believing that it has any meaning, or that we are somehow in control. We're not; the feeling of free will is just a other trick of qualia.
We don't know that either. We may be a collection of interacting consciousnesses arising from different organs that all pass around the baton called "I".
There's a lot of nerves and bacteria in the digestive system that might contribute some of it. That and various hormonal glands and reproductive systems.