... a philosophical problem devised by Frank Jackson to prove the existence of qualia.
Mary is a scientist who has never seen color. She has perfectly normal vision, but she has spent her life in a controlled color-free environment. She learns all that the physical sciences could ever hope to explain about color from black and white books and television. Upon her release, she experiences color for the first time. Jackson's argument is as follows:
- Mary (before her release) knows everything physical there is to know about other people.
- Mary (before her release) does not know everything there is to know about other people (because she learns something about them on her release).
Therefore,
- There are truths about other people (and herself) which escape the physicalist story.
(Thomas 1998)
My opinion
The problem I have with Jackson's so-called "Knowledge Argument" is that it is uses circular reasoning. Jackson "proves" that there are non-physical "truths" by excluding a person's subjective experiences (i.e. to "experience" color) from this complete knowledge/understanding of the physics of color. Additionally, he also makes the assumption that it is possible to have complete knowledge of anything.
References
Thomas, Nigel PhD. "Mary Doesn't Know Science:
On misconceiving a science of consciousness." http://www.calstatela.edu/faculty/nthomas/marytxt.htm
Tye, Michael; "Qualia", The Stanford Encyclopedia of Philosophy (Spring 2003 Edition), Edward N. Zalta (ed.), forthcoming URL = http://plato.stanford.edu/archives/spr2003/entries/qualia/
Thanks to mirv, arieh, KissThis, and Cletus the Foetus for clarifying some terminology.