A much discussed subject in analytical philosophical is the so-called “knowledge argument”. In order to explain what it involves, I’ll extensively quote from Frank Jackson’s article “What Mary Didn't Know”, which was the start of the present discussion:
“Mary is confined to a black-and-white room, is educated through black-and-white books and through lectures relayed on black-and-white television. In this way she learns everything there is to know about the physical nature of the world. She knows all the physical facts about us and our environment, in a wide sense of ‘physical’ which includes everything in completed physics, chemistry, and neurophysiology, and all there is to know about the causal and relational facts consequent upon all this, including of course functional roles. If physicalism is true, she knows all there is to know. For to suppose otherwise is to suppose that there is more to know than every physical fact, and that is just what physicalism denies. Physicalism is not the noncontroversial thesis that the actual world is largely physical, but the challenging thesis that it is entirely physical. ... It seems, however, that Mary does not know all there is to know. For when she is let out of the black-and-white room or given a color television, she will learn what it is like to see something red, say. This is rightly described as learning – she will not say ‘ho, hum.’ Hence, physicalism is false. This is the knowledge argument against physicalism in one of its manifestations. ... The knowledge argument does not rest on the dubious claim that logically you cannot imagine what sensing red is like unless you have sensed red. ... [It] is not that ... [Mary] could not imagine what it is like to sense red; it is that, as a matter of fact, she would not know. But if physicalism is true, she would know ...” (pp. 291-2; italics Jackson)
To summarize: Mary learns all physical facts that there are about, say, colour. However, Mary lives in a black-and-white world, so if she sees a ripe red tomato for the first time in her life, she learns something new about colour, namely what red is. So it is not possible to describe the world as if it is entirely physical. The upshot is that the thesis that the world is entirely physical is false, so Jackson in this article.
Now it is so that Jackson, who published his article about Mary in 1986 (and a related article in 1982), was not the first one to draw attention to this “knowledge argument”. Already in 1689 John Locke had put forward the same idea in his An Essay Concerning Human Understanding, and, for instance, in 1927 Bertrand Russell wrote “It is obvious that a man who can see knows things which a blind man cannot know; but a blind man can know the whole of physics. Thus the knowledge which other men have and he has not is not a part of physics.” (quoted from Crane 2019, p. 18) However, it was Jackson’s article that led to a long lasting discussion, which actually lasts till the present. Recently yet, Cambridge University Press published a book that examines the relevance of the knowledge argument in philosophy of mind today (Coleman 2019).
Here I don’t want to discuss this book, but most articles in it reject the knowledge argument. As I see it, the essence of Jackson’s article is that the idea that the world is entirely physical is false because of the knowledge argument. However, I think – and I am not the only philosopher who thinks so – that Jackson confuses two levels. One level is how the world is like; another level is how we know about the world. The first level is a matter of ontology (how things are), the second level is a matter of epistemology (how we describe and know about things). To take an analogy, look at this picture:
You can describe the colour of this square as pink. But even in case you see and describe this colour rightly as pink, you still don’t know how this pink is constituted. For it can be made by mixing the colours red, green and blue (RGB), but it can be made also by mixing the colours cyan, magenta, yellow and black (CYMK). Rightly interpreting the colour as pink and knowing how it is constituted are two different things. Ignoring the saturation, brightness and hue of a colour, this pink can be described technically by its RGB values 235-184-198. Alternatively it can be described also by its CMYK values 5-35-11-2. Nevertheless you don’t know how the colour is produced, if you know only the description. Analogously, a description of the world doesn’t say how the world is constituted. So, say, someone states that the world can be described entirely in physical terms, then the knowledge argument shows that this view is not right, but it doesn’t refute the view that the world is entirely physical.
I think that the thesis that the world is entirely physical is false. For example, meaning and culture are two non-physical phenomena. What red is like is another case in point. But this physicalism thesis is not false because of the knowledge argument.
- Frank Jackson, “What Mary Didn’t Know”, in: The Journal of Philosophy, Vol. 83, No. 5. (May, 1986), pp. 291-295.
- Sam Coleman (ed.), The Knowledge Argument. Cambridge: Cambridge University Press, 2019.- Tim Crane, “The Knowledge Argument is an Argument about Knowledge”, in Coleman (2019), pp. 15-31.