Knowledge and Reality
Scepticism
Lecture four: Semantic Externalism
Ema Sullivan-Bissett
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www.emasullivan-bissett.com
Feedback and Advice hour: Thursdays, 11:30, office A/101
(weeks 2–6)
Semantic Externalism
‘[T]he meaning and reference of some of
the words we use are not solely
determined by the ideas we associate
with them or by our internal physical
state’
(Lau and Deutsch 2010).
‘[M]eanings just aren’t in the head’
(Putnam 1981: 19).
Churchill and the Ant
‘An ant is crawling on a patch of
sand. As it crawls, it traces a line in
the sand. By pure chance the line
that it traces curves and recrosses
itself in such a way that it ends up
looking like a recognizable
caricature of Winston Churchill.
Has the ant traced a picture of
Winston Churchill, a picture that
depicts Churchill?’
(Putnam 1981: 1).
Similarity and Representation
• Similarity is neither necessary nor sufficient for representation.
• Not sufficient:
– the ant’s trace which resembled Churchill did not represent Churchill.
• Not necessary:
– printed words and spoken words can represent without resembling.
Intention and Representation
• What is necessary for representation?
• Intention.
‘Suppose the ant had seen Winston
Churchill, and suppose that it had the
intelligence and skill to draw a picture
of him. Suppose that it produced the
caricature intentionally. Then the line
would have represented Churchill’
(Putnam 1981: 2).
Mental Representation
‘Suppose there is a planet somewhere on which human
beings have evolved (or been deposited by alien spacemen,
or what have you). Suppose these humans, although
otherwise like us, have never seen trees. Suppose one day a
picture of a tree is accidentally dropped on their planet by a
spaceship which passes on without having other contact
with them. Imagine them puzzling over this picture. What
in the world is this? All sorts of speculations occur to them:
a building, a canopy, even an animal of some kind. But
suppose they never come close to the truth’
(Putnam 1981: 3).
Mental Representation
‘For us, the picture is a representation of a tree. For these
humans the picture only represents a strange object,
nature and function unknown. Suppose one of them
has a mental image which is exactly like one of my
mental images of a tree as a result of having seen the
picture. His mental image is not a representation of a tree.
It is only a representation of a strange object (whatever
it is) that the mysterious picture represents’
(Putnam 1981: 3–4).
Humans* do Represent Trees
• We can be externalist about representation, and still claim that
the humans* do represent a tree upon seeing/thinking about the
picture.
• We can say this because the right causal connection obtains
(providing the tree drawing was produced by a human being,
who had seen a tree).
• ‘There is a causal chain from actual trees to the mental image
even if it is a very strange one’ (Putnam 1981: 4).
HUMANS
TREE
DRAWING
TREE
HUMANS*
REPRESENTATION
OF A TREE
No they don’t!
(If we change the example)
• Remove the causal chain.
• Now the ‘picture’ dropped onto the humans*’ planet is not
a picture but ‘the accidental result of some spilled paints’
(Putnam 1981: 4).
• Now the ‘picture’ of a tree is as much a picture of a tree as
the ant’s ‘drawing’ is a drawing of Churchill (i.e., it isn’t!).
• Now the humans* ‘would still have mental images
qualitatively identical with my image of a tree, but they
would not be images which represented a tree any more
than anything else’ (Putnam 1981: 4).
Words
• Imagine a typed sentence featuring
a description of trees: ‘trees are
beautiful green delights’.
• Now imagine that sentence was
randomly produced by monkeys at
a type writer, hitting keys for
millions of years.
• Now the token of ‘trees’ in ‘trees
are beautiful green delights’ does
not refer to trees.
(Putnam 1981: 4).
The Japanese ‘Speaker’
• Imagine a person memorized the monkeys’ words
‘trees are beautiful green delights’, translated into
Japanese.
• Through hypnosis, the person mistakenly thinks he
understands the sentence.
• ‘[I]f he couldn’t use the words in the right contexts,
answer questions about what he ‘thought’, etc.,
then he didn’t understand them’ (Putnam 1981: 4).
Compare:
Turing’s (1950) Imitation Game
•
Interrogator, person, machine.
•
Separate the interrogator from the
person and the machine.
•
The interrogator’s aim: determine
which of the two respondents is the
person, and which is the machine.
•
The person’s aim: help the interrogator
correctly identify him (the person).
•
The machine’s ‘aim’: make the
interrogator mistakenly conclude that
it (the machine) is the person.
John Searle’s (1990) Response
The Turing Test for Reference
• The Turing Test for reference is designed to determine if the
interlocutor’s words refer.
• Once again: we have a conversation and…
‘[I]f no problems arise, if the partner ‘passes’ in the sense of being
indistinguishable from someone who is certified in advance to be
speaking the same language, referring to the usual sorts of objects, etc.,
[we] conclude that the partner does refer to objects as we do’
(Putnam 1981: 9).
• Is the Turing Test for Reference a definitive test for shared reference?
No
• ‘[I]t is not logically impossible […] that someone could pass the
Turing Test for Reference and not be referring to anything’
(Putnam 1981: 10).
• A machine programmed to produce English responses, with no
sense organs or motor organs could pass the Turing Test for
Reference.
‘[W]e cannot and should not attribute reference to such a device.
It is true that the machine can discourse beautifully about, say,
the scenery in New England. But it could not recognize an apple
tree or an apple, a mountain or a cow, a field or a steeple, if it
were in front of one. […] There is no more reason to regard the
machine’s talk of apples as referring to real world apples than
there is to regard the ant’s ‘drawing’ as referring to Winston
Churchill’
(Putnam 1981: 10–11).
Putnamian Brains in a Vat
‘Instead of having just one brain in a vat, we could
imagine that all human beings […] are brains in a
vat […] Perhaps there is no evil scientist, perhaps
(though this is absurd) the universe just happens to
consist of automatic machinery tending a vat full
of brains and nervous systems’
(Putnam 1981: 6).
Putnamian Brains in a Vat
• Automatic machinery exists by cosmic
chance or coincidence.
• The machinery has no intelligent creator –
all sentient beings are inside the vat.
Wright’s Observation
•
The standard Brain in a Vat scenario is consistent with our beliefs about the
external world being true—the alien/scientist tending the vat may not be a
deceiver. Putnam’s story is inconsistent with almost everything I believe about
the physical universe. So a sceptic’s argument using Putnam’s scenario is
simpler (it doesn’t need to additional claim that the alien/scientist is a deceiver):
‘The standard brain-in-a-vat fantasy is, whereas Putnam’s is not, consistent with
the truth of most of my beliefs about the material world. It may be that the
purposes of the Evil Scientist do not require him to be a deceiver, and that most
of the information I am fed is genuine. By contrast, Putnam’s version of a
world wholly constituted by a group of brains-in-a-vat and that attendant
automatic machinery is already inconsistent with almost everything I believe
about the physical universe. This discloses a more substantial consequence of
Putnam’s modifications to the standard story: an explicit sceptical argument
built upon Putnam’s version can be significantly simpler’
(Wright 1992: 69–70).
BREAK
Putnamian Brains in a Vat
‘Instead of having just one brain in a vat, we could
imagine that all human beings […] are brains in a
vat […] Perhaps there is no evil scientist, perhaps
(though this is absurd) the universe just happens to
consist of automatic machinery tending a vat full
of brains and nervous systems’
(Putnam 1981: 6).
Putnamian Brains in a Vat
• Let us suppose that the Putnamian brains in a vat
story is true. If it were, could we, as envatted
brains, say or think that this was the case?
• No (even though the situation is a physically
possible one, and one which is consistent with our
experiences).
• It cannot be true, because it is self-refuting.
Self-Refuting Suppositions
• Suppositions which if true, imply their own falsity.
• ‘All general statements are false’ (Putnam 1981: 7).
– ^ is a general statement. So if it is true, it is false.
• ‘I do not exist’ (Putnam 1981: 8).
– Entertaining of ^ makes it false.
– For any ‘me’, if it is thought by me, or said by me, it is false.
Putnamian Brains in a Vat
and Self-Refutation
‘The supposition that we are brains in a vat
has just this property. If we can consider
whether it is true or false, then it is not true
[…] Hence it is not true’
(Putnam 1981: 8).
Brains in Vats, ‘Trees’, and Trees
• The word ‘tree’ as used by these brains in the vat are not
connected to actual trees (run the counterfactual – they
would still use the word ‘tree’ exactly as they do even if
there were no actual trees outside of the vat!)
• For us, the brains in vats’ words do represent trees (but
qualitative similarity does not equal sameness of reference!)
‘[T]he brains in a vat are not thinking about real trees when
they think ‘there is a tree in front of me’ because there is
nothing by virtue of which their thought ‘tree’ represents
actual trees’
(Putnam 1981: 13).
Brains in Vats, ‘Trees’, and Trees
• Possible referents for the brains in vats’ thoughts,
utterances, or images of ‘trees’.
– Trees in the image.
– The electronic impulses that cause tree experiences.
– The features of the program that are responsible for those electronic
impulses.
‘These theories are not ruled out by what was just said, for
there is a close causal connection between the use of the
word ‘tree’ in vat-English and the presence of trees in the
image, the present of electronic impulses of a certain kind,
and the presence of certain features in the machine’s
program’
(Putnam 1981: 14).
‘We are brains in vats’
• If the possible world in which the Putnamian brains in vats
scenario is the actual world (i.e., if it really is the case),
when we say ‘we are brains in vats’, that means something
like
– ‘We are brains in the image.’
– ‘We are brains in the electronic impulses that cause vat experiences.’
– ‘We are brains in the features of the program that are responsible for
electronic impulses that cause vat experiences.’
‘So if we are brains in a vat, then the sentence ‘We are
brains in a vat’ says something false (if it says anything). In
short, if we are brains in a vat, then “We are brains in a
vat” is false’
(Putnam 1981: 15).
Objections to Putnam’s Argument
1. Standard BiV Argument
is Unscathed
• Putnam’s argument doesn’t work against the standard brain-in-avat story in which an evil scientist is manipulating my brain.
• If the scientist stimulates my brain to produce in me the
experience of seeing a tree, in the same way that his own brain is
stimulated when he sees a tree, I have sense impressions which
are exactly like his veridical sense impressions.
• This means that I really do represent a tree when my brain is
stimulated in such a way as to produce in me the experience of
seeing a tree, because my representation stands in a causal
connection to real trees.
TREE.
REPRESENTATION
OF A TREE
Standard BiV Argument
is Unscathed
‘Putnam's claims about reference, then, hold at best for
worlds in which there is nothing other than brains in a
vat and their automatic tenders […] So even if it
follows from Putnam's remarks that it is not possible
that I am in a vat of the latter sort, it does not follow
that it is not possible that I am a brain in a vat of the
standard sort. Hence Putnam's remarks have no force
against a Cartesian skeptical argument built upon the
(supposed) counterpossibility that I am a brain in a vat
of the standard sort’
(Brueckner 1986: 151–2).
2. Recent Envatment Not Ruled Out
• Putnam’s argument does not speak against the
possibility that I am a recently envatted brain.
• If I had been speaking English (as opposed to vatEnglish) up until the evil scientist took my brain,
then my words will continue to refer even when
I’m a brain in a vat (the right causal connections
for reference are still in place).
(Brueckner 2012).
REPRESENTATION
OF THE ROCKIES
REPRESENTATION
OF THE ROCKIES
But…
• The recent envatment scenario is not an ideal one for
the sceptic to employ, since in such a scenario:
‘the pertinent skeptical argument leaves unscathed
many of my knowledge-claims (such as that I was born
in the USA, that I own a black cat,…) So the “recent
envatment” scenario lacks the skeptical power of the
Putnamian BIV scenario’
(Brueckner 2012).
3. Only Metalinguistic
Knowledge Affected
I am a brain
in a vat.
False. Because the
brain is not ‘in a
vat in the image’
(for example).
Vat
English
I am a brain
in a vat.
False. Because
she is not a brain
in a vat.
English
3. Only Metalinguistic
Knowledge Affected
• The sentence ‘I am a brain in a vat’ has different truth conditions in
English and in vat-English, as such the sentence expresses different
propositions in the two languages.
• If I do not know whether I am speaking English or vat-English when I
say ‘I am not a brain in a vat’, then I do not know what proposition is
expressed by my utterance.
• But all this allows me to claim is that ‘the metalinguistic knowledge that
a certain sentence expresses a false proposition, rather than the objectlanguage knowledge that I am not a brain in a vat’.
• But it is knowledge of the object-language kind which Putnam needs to
refute scepticism.
(Brueckner 1986: 166–7).
3. Only Metalinguistic
Knowledge Affected
I am a brain
in a vat.
Vat
English
I am a brain
in a vat.
English
3. Only Metalinguistic
Knowledge Affected
Next
• Seminars:
– Do the reading!
– Come with at least one question per topic.
• Assessment:
– One 1500 word essay due noon on 10th
November (Monday week seven).
– Essay questions on the VLE.
References
Brueckner, Andrew 1986: ‘Brains in a Vat’. The Journal of Philosophy. Vol. 83, pp. 148–67.
----------------------------- 2012: ‘Scepticism and Content Externalism’. The Stanford Encyclopaedia of
Philosophy, available online at http://plato.stanford.edu/entries/skepticism-content
externalism/
Lau, Joe and Deutsch, Max 2010: ‘Externalism about Mental Content’. The Stanford
Encyclopaedia of Philosophy, available online at http://plato.stanford.edu/entries/content
externalism/
Putnam, Hilary 1981: ‘Brains in a Vat’ in his Reason, Truth and History. Cambridge:
Cambridge University Press.
Searle, John 1980: ‘Minds, Brains, and Programs’. Behavioral and Brain Sciences. Vol. 3, No. 3,
pp. 417–24.
Turing, Alan 1950: 'Computing Machinery and Intelligence'. Mind, Vol. 59, No. 236, pp. 433
–60.
Wright, Crispin 1992: ‘On Putnam’s Proof that we are not Brains-In-A Vat’. Proceedings of the Aristotelian
Society. Vol. 92, pp. 67–94.
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