[claudiosf1]

"Jackson’s thought-experiment about Mary challenges physicalism in the following way. Physicalists claim that physical science can fully explain consciousness. However, when Mary sees the red of the apple, says Jackson, she learns something new, despite having previously learnt all the physical facts about colour vision. Thus, argues Jackson, Mary has come to know a non-physical fact; so proving that not all knowledge is physical."

I can't see how this result proves anything. Consider the analogous experiment of "Mary learns to cycle by reading books". Surely she can learn all the physics behind cycling without truly knowing how to cycle, and one could similarly conclude that there is something beyond the physical mind behind this skill. Nevertheless, we can use reinforcement learning to teach an ANN to cycle, and that doesn't mean our robot has acquired a metaphysical consciousness.

You can still interpret both results from a physicalists perspective as in "some learnings require specific physical stimuli".

[Isinlor]

If she knows everything about colors then she could remove her retina and stimulate her visual nerve with the identical signal as color red would produce.

I'm 100% confident that she would experience red without actually seeing red.

Consider a separate thought experiment. A Bob lives in a bubble that does not allow liquids to exists outside his body. If he puts his hand in a completely dry glove sticking outside the bubble and surrounded by water he will experience wetness despite having no contact with water.

We know that our body does not have direct sensors of wetness. We experience pressure and heat loss as wetness. So you 100% can experience wetness without getting wet.

[riversflow]

I would argue, in the first case, stimulating your visual nerve with the identical signal as the color red would produce would be seeing red. Your argument is akin to saying that someone born profoundly deaf with a cochlear implant has never heard anything! Additionally, the phenomenon of "red" would seem to be more complex than just a single channel, any human will agree that (256,0,0) is not to the only RGB value that maps to red, but would Mary be able to identify which clouds in a sunset were orange, which red, which pink or purple?

For your second thought experiment, I would argue that wearing a wet glove is not a complete representation of wetness, because of the specific interactions that wetness has on the skin; apart from the sensations of pressure and heat loss, there is also the way that water moves/interacts with the skin making it more grippy, the texture of water and it's surface tension forming drips, and the movement of those drips, and the way wet skin feels different are all part of the overall qualia of wetness, hence why we differentiate between e.g. drenched and misted. There are 6 different mechanoreceptor systems in the skin, and the complete phenomenal concept of wetness likely involves all of them. I also think this is a poor thought experiment, because it necessarily involves water, image Bob exists in a plane of reality without liquid water entirely, would it be feasible for him to experience wetness?

[Isinlor]

> I would argue, in the first case, stimulating your visual nerve with the identical signal as the color red would produce would be seeing red. Your argument is akin to saying that someone born profoundly deaf with a cochlear implant has never heard anything!

I don't really object to that. My conclusion is that you can know what red is on the level of qualia without getting in contact with approximately red wavelength light. You can know what sound is without getting in contact with pressure waves. You can know what wetness is without getting in direct contact with water.

> I also think this is a poor thought experiment, because it necessarily involves water, image Bob exists in a plane of reality without liquid water entirely, would it be feasible for him to experience wetness?

I don't know. In that plane of reality we would not have evolved a mechanism for sensing wetness.

I don't know if it's possible to experience being in a spacial 2 dimensional reality or spacial 4 dimensional reality. My guess would be yes, but it would require significant alternations to our bodies, mostly brain structures.

Our experience of reality is almost certainly very limited vs. what's possible. There exist distinct human personalities who can see trough each other eyes and communicate with their minds - I'm talking about craniopagus twins.

I'm looking forward to high-bandwidth computer-brain interfaces. Some people may actually get to experience how it is to be a computer or whether it feel like anything at all.

[Quekid5]

It honestly sounds like a lot of conflating "learning/recognizing X" for "experiences X" (even going so far as to invent a new word, qualia, for that)... which just seems like a bizarre distinction to me.

[hdjjhhvvhga]

> So you 100% can experience wetness without getting wet.

Which leads us to the interesting conclusion "you can experience everything without actually experiencing it" which is a bit Buddhist.

[nkrisc]

What is “wet” then? Liquid clinging to your skin through surface tension and other forces? If your hand is submerged in a liquid that will not cling to your skin at all, is your hand “wet” while it is still submerged? You’d feel “wetness” according to your definition but your hand would be “dry” when you remove it. I don’t think wetness is defined by future state, but by present state.

If Bob is experiencing wetness, then he is “wet”, at least while he experiences it, even if his hand will be dry when he removes it from the glove.

[Isinlor]

> What is “wet” then? Liquid clinging to your skin through surface tension and other forces?

Yes.

> If your hand is submerged in a liquid that will not cling to your skin at all, is your hand “wet” while it is still submerged?

No. If you submerge your hand in mercury you will not get wet. The same if you coat you hand in aerogel. It is empirical fact that people do not describe this situations as being wet.

E.g.: https://youtu.be/GcdB5bFwio4?t=225

[MrsPeaches]

> If you submerge your hand in mercury you will not get wet.

Tangent: To what extent is that evolutionary? Wetness being a unique feeling could be, that we have evolved a greater sensory capacity to experience water, due to its abundance and importance.

Thus other words for touch (in English) generalise across a variety of sensory experiences (sticky, slimy, hard, etc.) where as wetness is specific to fluids that behave like water.

If I had a point, I guess it would be that maybe wetness is a especially unique experience. I don’t know whether this makes it a better or worse example to use.

[nkrisc]

Yes, exactly.

Then, having worn a nitrile glove while putting my hand in water before, I doubt that Bob would experience wetness.

Easily tested at home.

[Isinlor]

I distinctly remember a situation where I was being confused whether my hand was wet or not when wearing gloves. My hand was in fact not wet back then. I went to test it again to refresh my memory and the experience in glove is not identical, but it is certainly sufficiently close to have a potential to confuse. Especially when submerging a hand with glove and without glove the experience is very similar, the biggest difference is when you get the hand out of the water.

The glove provides quite a good approximation.

[nkrisc]

It’s similar, but it’s not the same. I’m not yet ready to accept that the sensation of “wet” is only the result of pressure and heat transfer. Which is why, though similar, you can still tell the difference.

[TheBigSalad]

Exactly, or maybe she simply saw a red apple in her dream. You can think if people as robots and the eyes are sensors that tickle the brain with the red signal. It can happen without actually seeing red. We know this because we have dreams and they are all sorts of sensory experiences that are completely made up by our computer brains.

[lolc]

I don't think people who have never seen red can dream of red. Color vision is acquired as far as I know. Newborns don't have it in the sense that they have to train to distinguish colors.

As such, I find it entirely plausible that Mary would be too old to learn color vision. Much like people born blind cannot acquire full vision later. She might just be unable to experience red. That would include her dreams.

Yes stimulatimg her optical nerves could prepare her to see red. Meaning she'd jave the brain hooked up the right way to see it.

[naasking]

> I can't see how this result proves anything. Consider the analogous experiment of "Mary learns to cycle by reading books". Surely she can learn all the physics behind cycling without truly knowing how to cycle, and one could similarly conclude that there is something beyond the physical mind behind this skill.

This is indeed one of the standard responses to Mary's Room, where experiences like "redness" are not actually knowledge but are an "ability". So Mary doesn't actually "learn" anything new technically, but she acquires a new ability to experience redness when exposed to it for the first time.

[pdonis]

> I can't see how this result proves anything.

It doesn't. When you dig into the details, Jackson's argument is circular: he can only infer that Mary learns something new by implicitly assuming it.