February 20, 2017 // By Matthew Owen
This is a bad, but short post about a good argument. It’s bad because it almost entirely consist of a quote, but a good quote. (So perhaps the post is decent on balance?) The quote is from Frank Jackson’s article ‘Epiphenomenal Qualia.’ It’s Jackson’s famous knowledge argument against reductive physicalism in a nutshell (please don’t picture Austin Powers stuck in nutshell).
If reductive physicalism were true, then knowledge of all the physical facts relevant to conscious visual perceptions would entail knowledge of all facts about conscious visual perceptions. Using the following fictional story about a neuroscientist, Jackson (1982, p. 130) argues that knowledge of all the physical facts doesn’t entail knowledge of all the facts about visual perceptions.
Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specialises in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like ‘red’, ‘blue’, and so on. She discovers, for example, just which wave-length combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal chords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue’. (It can hardly be denied that it is in principle possible to obtain all this physical information from black and white television, otherwise the Open University would of necessity need to use colour television.)
What will happen when Mary is released from her black and white room or is given a colour television monitor? Will she learn anything or not? It seems just obvious that she will learn something about the world and our visual experience of it. But then it is inescapable that her previous knowledge was incomplete. But she had all the physical information. Ergo there is more to have than that, and Physicalism is false.
That’s the knowledge argument in short. Again, if (A) reductive physicalism were true, then (B) knowledge of all the physical facts relevant to conscious visual perceptions would entail knowledge of all facts about conscious perceptions. Through this thought experiment Jackson argues that (¬B) knowledge of all the physical facts doesn’t entail knowledge of all the facts about visual perceptions. What follows is: (¬A) reductive physicalism is false. The rest is, as they say, a song and a dance…and of course responding to objections.
Featured image credit: Perception by Steve Rotman. CC-BY-NC-ND 2.0 via flickr. Image cropped.