Philosopher Frank Jackson (1943–) is known for his argument against physicalism. Physicalism is the view that the universe is entirely physical – that the world can be completely and accurately described in the language of physics. Anything that physics could not describe, then – things like God and souls – does not exist if physicalism is true.
Jackson’s argument is put to us in the form of a thought experiment involving an extremely clever neuroscientist named Mary. For whatever reason, Mary has spent her entire life confined to a black and white windowless room in which she only receives information about the outside world through a black and white TV. Poor Mary has therefore never seen any colour. Being a brilliant scientist, Mary nonetheless manages to teach herself every single physical fact there is to know about colour vision using only some books and information from the TV. She knows, e.g., exactly what happens with wavelengths of light, and retinas, and brain processes, and so on and so forth. Now imagine that one day Mary escapes from the room. Before stepping outside, Mary knows all the physical facts there are to know about seeing colour. But ask yourself: does Mary learn something new once she’s released into the world of colour? Intuitively, she does come to acquire some information that was previously unknown to her: she learns what it’s like to see colour. There is significance for physicalism if Mary does learn something new on her stepping outside, because whatever Mary comes to know is, by hypothesis, not describable in the language of physics. If it was so describable, Mary would have known it before leaving the room. Therefore, says Jackson, if there’s something about our mental life that physics can’t explain, the world cannot be entirely physical! | |||