Argument against physicalism

Mary's room, also known as Mary the super-scientist, is a thought experiment proposed by Frank Jackson in his 1982 article Epiphenomenal Qualia, and extended in What Mary Didn't Know, 1986. The experiment is intended to motivate what Jackson called the Knowledge Argument against physicalism

The debate that arose from its publication has led to an anthology entitled There's Something About Mary, published in 2004, and which includes responses from philosophers such as Daniel Dennett, David Lewis and Paul Churchland.

 

The thought experiment

The passage where Jackson introduced the thought experiment says:

 

Mary is a brilliant scientist who is, for some reason, forced to investigate the world from a black and white room through a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let's say, all the physical information there is to get about what happens when we see ripe tomatoes, or the sky, and uses terms like "red", "blue" and so on. She discovers, for example, just what combination of waves from the sky stimulate the retina, and exactly how this produces through the nervous system the contraction of the vocal cords and the expulsion of air from the lungs that results in the pronunciation of the sentence " the sky is blue". [...] What will happen when Mary is released from her black and white room or given a television with a color monitor? Will she learn something or not? It seems obvious that she will learn something about the world and our visual experience of it. But then it is undeniable that her prior knowledge of her was incomplete. But she had all the physical information. Ergo there is something more to have than that, and "physicalism" is false.

In other words, Mary is a scientist who has all the physical information about colors, but she has never experienced colors. The question is: once she experiences colors, will she learn anything new? If the answer is yes, then it means that physical information is not all there is to know about the world, and therefore physicalism is false. The argument can be reconstructed like this:

 

Mary has all the physical information about human color vision before she is released.

But there is some information about human color vision that Mary did not possess before she was released.

Therefore, not all information about human color vision is physical.

 

Daniel Dennett

Daniel Dennett argues that in fact, Mary would not learn anything new when she left the room in black and white and saw the color red. Dennett claims that if she really knew "all about colors," that knowledge would necessarily include a deep understanding of why and how human neurology makes us feel the qualia of colors. Therefore, she Mary would already know exactly what to expect from the color red, even before she leaves the room. Dennett argues that although we cannot conceive of such profound knowledge, if the unrealistic premise of the thought experiment is that Mary knows everything there is to know about colors, we cannot assume that because we cannot conceive or describe such knowledge, that knowledge is impossible. Consequently, Dennett concludes that the experiment does not provide a solid argument for the existence of qualia.

 

However, Frank Jackson, as emerges from the preceding quotes themselves, does not hypothesize that Mary knew "all about colors," but only that she has "all the physical information" (emphasis added). Otherwise, that the experience of colors involves more than just physical information about them. Dennett's argument is a clever play on words, but he fails to really replicate Jackson's postulate.