iii) Knowledge By Description & Knowledge by Acquaintance
iv) Mary's New Abilities
v) Knowing How & Knowing That
Mary “doesn't know what it's like to see red”. This argument has nothing to do with imagination (or Mary’s inability to imagine red). As Frank Jackson puts it: “Powers of imagination are not to the point”. This is about Mary’s knowledge (or lack thereof), not her imagination. More precisely, “she would not know” what it's like to experience red. More to the point,
“if physicalism is true, she would know; and no great powers of imagination would be called for”.
The first response to this is to ask what Jackson meant by the word “knowledge” (or by the words “knowledge of red”). This seems like an odd use of the word “know”. How would Mary (or anyone else for that matter) know what red is like? What is the epistemology of knowing red? Even if Mary could sense red: could she also know red (or what red is)? Could she (or anyone else) be wrong about what is or isn't red (i.e., without inter-communal responses)?
Is Jackson’s conclusion correct? That is:
i) If physicalism is true
ii) then Mary would know what red is.
Firstly, Jackson argues that given Mary’s “fantastic grasp of neurophysiology and everything else physical” she couldn't thereby work out the last phenomenal part of red “by making some more purely logical inferences”. Mary can't, then, infer the phenomenal from the purely physical - no matter how complete and exact her physical knowledge is.
Knowledge By Description & Knowledge By Acquaintance
Jackson then makes a distinction which has often been made in various areas of philosophy: the distinction between “knowledge by description” and “knowledge by acquaintance”. Presumably Mary had knowledge by description before she was let out of her black-and-white room. After she was let out, then she had knowledge by acquaintance. In other words, her previous complete descriptions of red weren't enough. On freeing, she also became acquainted with red (not only with red’s physical “supervenience base”, as Jaegwon Kim puts it).
Does this also mean that phenomenal red literally can't be described? This is a position which has been long accepted by many philosophers. That's why colours (or “colour words”) are taught (so the argument goes) purely by ostension – by the teacher pointing to something red and then saying to the student, “This is red.” However, if red is (in effect) purely phenomenal, and taught by ostension, then how can Mary (or anyone else) have knowledge of red?
Mary Acquired New Abilities, Not New Knowledge
I've questioned Jackson’s use of the notion of knowledge. So too does David Lewis and Laurence Nemirow. They do so by distinguishing knowing (or learning) that something is red from acquiring “a certain representational or imaginative ability”. How can the sudden new experience of red (outside the black-and-white room) be a knowledge of red? How does Mary learn something new? She experiences something new; though she doesn't learn something new or acquire new knowledge.
However, something new does happen to Mary. As stated, she acquires a certain representational or imaginative ability. Presumably that ability is to recognise red on further occasions (or to distinguish red from other colours). Though how would she know that it's red unless someone else tells her that's the case? This would be especially relevant if Mary's new experience of red was sudden and had no direct connection to her previous examinations of red’s physical micro-structure. Outside the room she would see something new; though how would she know that it's red? Indeed how would she have known that it was a colour of any description?
Knowing How & Knowing That
Earlier I commented on Jackson’s use of the knowledge by description and knowledge by acquaintance distinction. Now he brings in the “knowing how” and the “knowing that” distinction (as used by David Lewis).
Mary now knows how to recognise red. She has that “ability”. Does she know that it's red? Not if, as argued, she has no new knowledge of red at all. And even with such knowledge, she would still require third-person help (as it were) to tell her that the red wall outside is indeed red.
We can join up the two oppositions here:
knowledge by acquaintance - knowledge how
knowledge by description - knowledge that
However, according to this discussion, neither knowledge by acquaintance nor knowing how are, in fact, examples of knowledge (strictly speaking). Only knowledge by description and knowing that are true examples of knowledge. Alternatively, perhaps we can't have one without the other. That is:
i) We can't have knowledge how without knowledge that. Or,ii) We can't have knowledge that without knowledge how.
Mary needs knowledge that red is red before she can learn how to distinguish red from other colours. Alternatively, she must know something in order to know that it's a colour or that she has had a new experience outside her room. To know that red is red, she must know what red looks like. How does this work for the other distinction? Thus:
i) We can't have knowledge by acquaintance without knowledge by description. Or,ii) We can't have knowledge by description without knowledge by acquaintance.
This works in a similar way to the above - and for similar reasons. How do we know we're acquainted with something (an x) without the help of some form of description? How do we know we're now acquainted with red without some kind of ostensive definition (or some other kind of help)? We may know that we're acquainted with something new; though not that it's red or even that it's a colour of any kind. Alternatively, red can't be described to us in order to give us knowledge that without our also being acquainted in some way with phenomenal red. Without being acquainted with something, we wouldn’t know what it is that's being described.
Yet what if both distinctions are false disjunctures between ostensibly two alternatives? Perhaps this is like Ned Block’s distinction between “phenomenal consciousness” and “access consciousness”. The difference here is that Block admits that in this case you may not be able to have the one without the other. Nevertheless, this shouldn't stop us making the distinction because it's still, after all, an acceptable distinction.
The important conclusion to all this is that
“a physicalist can admit that Mary acquires something very significant of a knowledge kind – which can hardly be denied – without admitting that this shows that her earlier factual knowledge is defective”.
Physicalists aren't, then, denying that extra little something. They only deny the increase in Mary’s knowledge. Thus it's strange that Jackson (at least at this point in his career) still insisted in using the word “knowledge” - suitably reduced to his “of a knowledge kind”. What did he mean by that? A kind of knowledge is still an example of knowledge, isn’t it?
Thus perhaps all this depends on what Jackson and physicalists mean by the word “knowledge”!
Block, Ned, 'On a Confusion About a Function of Consciousness' (1995)
Jackson, Frank, 'What Mary Didn't Know' (1986)
Lewis, David, 'What Experience Teaches' (1990).