Explain Jackson's Knowledge Argument and why it could pose a problem for physicalist accounts of mind.

Jackson’s Knowledge Argument is used by opponents of physicalism to cast doubt upon the physicalist’s central claim, that talk of the mental can be reduced to talk purely of the physical. I will now set about explaining the argument itself, in order to illustrate how it causes a problem for physicalist accounts of the mind. Jackson asks one to suppose there is a neuroscientist called Mary. Mary is an expert in the physics of colour and how human beings perceive it. She can identify the different physical properties of colour perception in the brain as well as how colour travels through light. Despite this expert knowledge of colour, Mary operates in a black and white laboratory, which she has never left. Mary understands fully the physical structures of colour but has never seen one herself. Jackson then asks one to suppose the Mary leaves the black and white lab and enters the world. She, for the first time, personally engages in colour perception. Jackson argues that in doing so, Mary learns something new – what it is actually like to see colour. He maintains that Mary, despite knowing everything about the physical properties of yellow, did not know what it was like to experience the qualitative sensation of seeing the yellowness of a yellow daffodil. Proponents of materialism would dispute this claim, arguing that Mary had not learnt anything new about the colour yellow. However, this seems counter-intuitive, as it seems obvious that Mary could not have known what it was like to see yellow prior to leaving the laboratory.

If one is to accept Jackson’s argument, then it undermines physicalism’s central claim – that talk of the mental can be purely reduced to talk of physical matter or processes. The argument does this, as if the act of perceiving colour gives the perceiver knowledge that otherwise could not be explained in purely physical terms, then there must be something about human conscious experience of colour that is non-physical. By accepting this position, one cannot therefore support a physicalist account of the mind, as it is a position that is fundamentally contrary to physicalism’s central tenet.