What Mary didn't know - Frank Jackson

 

Jackson_MaryDidn'tKnow.pdf

The Journal of Philosophy, Vol. 83, No. 5. (May, 1986), pp. 291-295.


§ Jackson's Knowledge Argument:

___ 1. Physicalism is the challenging thesis that the actual world is entirely physical.
___ 2. Thus under physicalism, complete physical knowledge is the complete
knowledge of the actual world.
___ 3. However, a physicist Mary could know all there is to know about the physical
nature of the world, while not knowing the qualia of others' experiences.
___ 4. Hence, physicalism is false.
* On Physicalism:
___ The claim is that if physicalism is true, then if you know everything expressed or
expressible in explicitly physical language, you know everything.
[Question]:
___ Can we claim that every object and every event is a physical object and a
physical event while at the same time deny that a complete physical language can
explain everything?
Namely: Can we have the following distinction [Liu]:
Weak Physicalism[WP] (i) Every object and event in our world is a physical
object and a physical event in the sense that there is
nothing that is not governed by physical laws.
Strong Physicalism[SP] (i) WP.
(ii) Every event and property in our world is either
explicable in terms of physical laws, or explanatorily
reducible to physicalistic explanation.
* On Mary's Knowledge:
Jackson's Claim:
___ Mary does not know all there is to know.
___ The trouble for physicalism is that, after Mary sees her first ripe tomato, she
will realize how impoverished her conception of the mental life of others has been all
along. She will realize that there was, all the time she was carrying out her
laborious investigations into the neurophysiologies of others and into the functional
roles of their internal states, something about these people she was quite unaware of.
[Question]: Do you agree that Mary lacks a certain knowledge about facts of the
world?
§ Three Clarifications
[A] 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 that, as a
matter of fact, she would not know.)
[B] The intensionality of knowledge is not to the point. The argument does not rest
on assuming falsely that, if S knows that a is F and if a = b, then S knows that b is F.
___ Endowing her with great logical acumen and persistence is not in itself enough
to fill in the gaps in her knowledge.
[C] The knowledge Mary lacked is knowledge about the experiences of others, not
about her own.
§ Objections and Jackson's Reply
(i) Churchland's formulation of the knowledge argument:
(1) Mary knows everything there is to know about brain states and their
properties.
(2) It is not the case that Mary knows everything there is to know about
sensations and their properties.
Therefore, by Leibniz's law:
(3) Sensations and their properties ≠ brain states and their properties.
* Jackson's Reply:
___ The whole thrust of the knowledge argument is that Mary does not know everything
there is to know about brain states and their properties, because she does not know about
certain qualia associated with them. What is complete, according to the argument, is her
knowledge of matters physical.
* Jackson's Reformulation of the knowledge argument:
(1) Mary (before her release) knows everything physical there is to know
about other people
(2) Mary (before her release) does not know everything there is to know
about other people (because she learns something about them on her
release).
(3) Therefore, there are truths about other people (and herself) which escape
the physical story.
(ii) David Lewis' Objection:
___ What Mary acquires when she is released is a certain representational or imaginative
ability; it is knowledge how rather than knowledge that.... She knew all that there was
to know about the experiences of others beforehand, but lacked an ability until after
her release.
* Jackson's Reply:
___ (i) Her representational abilities were a known constant throughout.
___ (ii) What Mary acquires on her release is factual knowledge about the experiences of
others.
§ DISCUSSION QUESTION:
____ If Jackson is against physicalism, is he then a dualist?
____ Why does he take the approach emphasizing on a "knowledge gap" if he is
against the ontology of physicalism?
____ Has Jackson's knowledge argument really prove that physicalism is false?