McEvoy was shedding some doubts about the validity of the 'brain-in-a-vat'
thought experiment. A different formulation may be:
-- Let “P” stand for any belief or claim about the external world, say,
'Snow is white'.
ARGUMENT:
1) If I know that p, I know that I am NOT a brain in a vat.
2) I do not _know_ that I am _not_ a brain in a vat.
---- 3) Therefore, I do not know that p.
Putnam’s argument is designed to attack the possibility of global
skepticism.
The argument derives from Putnam's definifition of Realism.
Putnam defines Realism as the view which holds that
"the world consists of some fixed totality of mind-independent objects."
"There is exactly one true and complete description of ‘the way the world
is.’"
"Truth involves some sort of correspondence relation between words or
thought-signs and sets of things."/
This construal pf Realism brings out the idea that for Realism, truth is
not reducible to epistemic notions but concerns the nature of a
mind-independent reality.
Putnam's definition of Realism finds an accurate target in those scientific
materialists who believe in a "ready-made" world of scientific kinds
independent of human classification and conceptualization.
There are, however, many self-professed Realists who are not THAT happy
with Putnam’s conceptual analysis of Realism.
These Realists complain that Putnam's conceptual analysis saddles the
Realist with the admittedly difficult question of matching words to objects
and
of providing for a correspondence relation between sentences and
mind-independent "facts."
The Realist is further forced to construe the thesis ontologically, as an
adherence to some fixed furniture of objects in the world.
This ignores the possibility that ontological commitment may be specified
not as a commitment to a set of entities but rather to the TRUTH of a class
of sentences or even of WHOLE THEORIES of the world.
One alternative is to construe Realism as the position that there are NO a
priori epistemically derived constraints on reality.
By analysing the concept of Realism negatively, the Realist sidesteps the
thorny problems concerning correspondence or a "ready made" world, and
shifts the burden of proof on the challenger to refute the thesis.
Putnam’s Realist states that truth and reality can NOT be subject to
"epistemically derived constraints."
The major premise that underwrites Putnam’s argument is what he calls a
"causal constraint" on reference:
A term refers to an object only if there is an appropriate causal
connection between that term and the object.
To understand this causal constraint we need to unravel, obviously, what
Putnam means by "appropriate causal connection."
If an ant were to accidentally draw a picture of Winston Churchill in the
sand, few would claim that the ant represented or referred to Churchill.
Similarly, if I accidentally sneeze
"Genghis Khan"
just because I verbalise the words does not mean that I refer to the
infamous Mongolian conqueror, for I may have never heard of him before -- and I
hold no M-intention as I 'utter' "Genghis Khan."
Reference cannot simply be an accident.
Or, as Putnam puts it, words do not refer to objects "magically" or
intrinsically. -- Reference involves very complex Griceian intentions, as S. R.
Schiffer in an essay in "Synthese" has pointed out.
Now establishing just what would count as necessary and sufficient
conditions for a term to refer to an object turns out to be tricky business.
There have been many "causal theories" of reference supplied to do just
that -- mpst inspired by Grice, "Causal Theory of Perception".
Many have taken the virtue of Putnam’s causal constraint to be its
generality.
Putnam's causal constraint merely states a necessary condition for
reference and need not entail anything more controversial.
Sometimes it is claimed that endorsing Putnam's causal constraint commits
you to semantic externalism.
But the issues are more complex, since an Internalist can agree with the
causal constraint.
With the causal constraint established, Putnam goes on to describe the
Brain in a Vat scenario.
It is important to note exactly what the thought-experiment is, for failure
to appreciate the ways in which Putnam formulates his thought-experiment
has lead to many mistaken "refutations" of the argument -- or rather
refutations which are better called 'refudiations', and, worse, of Putnam,
rather
than his argument.
Putnam has a mad-scientist -- he does not provide a surname for him --
envatting brains in a laboratory.
As a second step, this mad scientist, whose surname Putnam does not
disclose ("perhaps he does not exist") induces a virtual reality through a
sophisticated computer programme.
There is an important difference between viewing the brain from a
grammatical first or third person view-point. ("The mad scientist will use the
third person, but if I am a brain in a vat I should be allowed to use the
first
person.")
There is the point of view of the brain in a vat (henceforth BIVs), and the
point of view of the mad scientist, who cleverly remains outside the vat.
Clearly when the mad-scientist utters,
That is a brain in a vat.
he would be saying something true -- no matter what the brain in a vait
may mean (in Grice's use of 'mean') when the brain "says" that it itself is a
brain in a vat.
Furthermore, presumably a brain in a vat could sadly pick up referential
terms by borrowing them from the mad scientist.
Thus when a brain in a vat utters
There is a tree.
-- referring to a SIMULATION of a tree, it would be saying something
FALSE, since the brain's term "tree," that the brain sadly picked up from the
mad scientist to refer to an actual tree, or a real tree (if one may use
Austin's sexist trouser word), in fact refers to something else, like the mad
scientist's sense-impressions of a tree.
Putnam then stipulates that all sentient beings are brains in a vat, hooked
up to one another through a powerful computer that has no programmer.
"That’s just how the universe is," Putnam says.
We are then asked, given at least the physical possibility of Putnam's
thought experiment, whether we could say or think it.
Putnam answers that we could not.
The assertion,
We are brains in a vat.
or
"I am a brain in a vat".
-- would be "self-refuting" in the same way that the general statement "all
general statements are false" is -- but NOT "All generalisations are
hateful, including this one."
Putnam's thought-experiment stipulates that a brain in a vat would have
qualitatively identical thoughts to those unenvatted, or at least it has the
same "notional world."
The difference is that in the vat-world, there are no external objects
(other than the vat as McEvoy points out -- Putnams sometimes, to enrich his
style, calls the vat a jar).
When a brain in a vat utters,
There is a tree in front of me.
there is in fact no tree in front of the brain, only a simulated tree
produced by the computer’s program.
However, if there are no trees, there could be no causal connection between
the brain's tokens of trees and actual trees.
By Putnam's causal constraint, the brain's use of "tree" does not refer to
a tree.
This leads to some interesting consequences for the brain. (Putnam called
it a brain teaser).
A standard reading of a brain's utterance,
"There is a tree."
would have the statement come out FALSE, since there are no trees that the
brain is referring to.
But that would be only assuming that "tree" refers to a tree in the brain's
language -- that Putnam calls "Vatese".
If "tree", as used by the brain, does not refer to a tree, the semantic
evaluation of the sentence becomes unclear -- even to Grice. (Perhaps he
should have written, "Brain-in-Vat's Intentions and Meaning", to shed light on
this. Perhaps the brain is only disimplicating the mad scientist's use of
'tree').
Sometimes, Putnam suggests that a brain's tokens refer to an images or a
sense-impression. Putnam seems to be referring to Paul, "Is there a problem
about sense data?"
At other times Putnam seems to be claiming the truth-conditions would be
the facts about the electronic impulses of the mad-scientist's computer that
are causally responsible for producing the sense-impressions.
Indeed, Putnam has a good reason to choose these alternative
truth-conditions.
Through Grice's principle of charity, we would want to interpret the
brain's sentences to come out true ("Do not say what you believe to be false"
-- the most important of Grice's 'conversational maxims') but we would not
want the truth-conditions to be merely phenomenalistic (cfr. Paul, "Is there
a problem about sense data?")
Thus it turns out that when a brain says,
There is a tree in front of me.
the brain is saying something true — if in fact the computer is sending the
right impulses to it.
Another suggestion is that the truth-conditions of the brain's utterances
would be empty: the brain would not be asserting anything at all.
This *seems* to be rather strong.
However, surely the brain would mean something when it utters
There is a tree in front of me.
-- even if its statement gets evaluated differently because of the radical
difference of its environment.
One thing is clear, however.
A brain's tokening of "tree" would have a different reference assignment
from that of a non-envatted brain’s tokenings.
According to Putnam's causal constraint condition, my tokening of "tree"
refers to a tree because there is an appropriate causal link between it and
an actua (or "real", to use Austin's sexist trouser word) tree (assuming of
course I am not a brain in a vat).
A brain in a vat, however, would NOT be able to refer to a real or actual
'tree' since there is no tree (and even if there is a tree it would not be
the appropriate causal relation between its tokenings of 'tree' and a real
tree, unless we assume the brain picked up the term 'tree' from the mad
scientist).
Now one might be inclined to think that because there are at least brains
and vats in the universe, a brain would be able to refer to brains and
vats.
But the tokening of 'brain' is never actually caused by a brain except only
in the very indirect sense that its brain causes all of its tokenings.
The minimal causal constraint ensures that 'brain' and 'vat' (or 'jar' as
Putnam sometimes puts it to vary his prose) in "Vatese" does not refer to a
brain or a vat.
We are now in a position to give the logical form of Putnam’s argument.
It has the form of a conditional proof.
Assume we are brains in a vat.
If we are brains in a vat, 'brain' does not refer to a brain, and 'vat'
does not refer to a vat (via causal constraint)
If 'brain in a vat' does not refer to a brain in a vat, 'We are brains in
a vat' is false.
---- Therefore, if we are brains in a vat, the sentence 'We are brains in
a vat' is false.
Putnam adds, for good measure, that “We are brains in a vat" is
NECESSARILY false, since whenever we assume it is true we can deduce its
contradictory.
The argument is valid and its soundness depends on the truth of its
premises, assuming of course Putnam's causal constraint is true.
One immediate problem is determining the truth-conditions for 'We are
brains in a vat' on the assumption we are brains in a vat, speaking Vatese and
not English.
From Putnam's causal constraint we know that 'brains in a vat' does not
refer to brain in a vat.
But it doesn’t follow from this alone that 'We are brains in a vat' is
totally false.
Compare:
"Grass is green" is true iff grass is green
"Grass is green" is true iff one has sense-impressions of grass being green
"Grass is green" is true iff one is in electronic state Q
On the assumption that we are brains in a vat, Putnam's causal constraint
would appear to rule out this.
"Grass" does not refer to grass since there is no appropriate causal
connection between "grass" and actual grass.
Thus the truth-conditions for the statement "Grass is green" would be
non-standard.
If we take them to be those as captured above, "Grass is green", as
uttered by a brain in a vat would be true.
Consequently the truth-conditions for "We are brains in a vat" would be
similarly captured and turn the utterance true.
'We are brains in a vat' is true iff we have sense impressions of being
brains in a vat
On another construal of the truth-conditions, 'We are brains in a vat', as
uttered by a brain, would presumably be false, since a brain in a vat
would not have sense-impressions of being a brain in a vat.
Recall an envatted brain's notional world would be equivalent to the
unenvatted, and it would appear to itself to be a normally unenvatted brain.
However, if we adopt the truth-conditions above, we would have the
following:
"We are brains in a vat" is true if and only if we are in electronic state
Q
Now it is no longer clear that "We are brains in a vat" turns out to be
false.
For if the brain is in the appropriate electronic state, the
truth-conditions could well be fulfilled.
There are other reconstructions of the argument that do not depend on
specifying the truth-conditions of the envatted brain's utterance, and others
that depend on the envatted brain's IMPLICATURE (usually with reference to
the mad scientist, of course).
What is important is the idea that the truth-conditions would be as in:
"We are brains in a vat" is true if and only if we are brains in a vat.
Now we can construct the following conditional proof argument:
Assume we are brains in a vat.
If we are brains in a vat, "We are brains in a vat" is true if and only we
are brains in a vat.
If we are brains in a vat, we are not brains in a vat.
If we are brains in a vat, "We are brains in a vat" is false.
If we are brains ina vat, we are not brains in a vat.
Notice that the argument leaves the antecedent of the conditional open --
an "open subjunctive", to use Wright's wording -- vide Putnam, "Reply to
Wright".
But we do not want the premises of the argument to be counterfactual,
following the train of thought:
If we were brains in a vat, the causal constraint would entail that my
words ‘brain in a vat’ would come to denote something different.
For then we would be assuming that we are not brains in a vat, when that is
what the argument is supposed to prove.
Nevertheless, there are still problems.
Even if, by virtue of Putnam's causal constraint, the sentence "We are
brains in a vat" is false, an intuitive objection runs that this change of
language should not entail falsity of the proposition that we are brains in a
vat.
Either I am a brain in a vat or I am not a brain in a vat.
If I am a brain in a vat, "I am a brain in a vat" is true iff I have sense
impressions of being a brain in a vat.
If I am a brain in a vat, I do not have sense-impressions of being a brain
in a vat.
If I am a brain in a vat, "I am a brain in a vat" is false.
If I am not a brain in a vat, "I am a brain in a vat" is true iff I am a
brain in a vat.
If I am not a brain in a vat, "I am a brain in a vat" is false.
Therefore, "I am a brain in a vat" is false.
Putnam makes it clear that he is not, like Humpty Dumpty, merely talking
about semantics.
Putnam wants to provide a metaphysical argument that we can NOT be brains
in a vat, not just a semantic one that we cannot assert we are.
If Putnam is just proving something about Griceian utterer's meaning, it
is open for the sceptic to say that the bonds between language and reality
can diverge radically, perhaps in ways we can never discern. (Grice once had
that nightmare; he dreamed that he was a brain in a vat, but this was after
the Central meeting of the American Philosophical Association, where he
chaired a colloquium between Putnam, Wright, "and an actual brain in a vat
that we brought from a local hospital."
One response to this is to formulate two different arguments: one whose
meta-language is in English, the other whose meta-language is in Vatese, and
show that distinct arguments can be run to prove that "I am a brain in a
vat" is false, or at least conversationally odd.
One may go as follows:
My language disquotes.
In Vatese, "brains in a vat" does not refer to brains in a vat.
In my language, "brains in a vat" is a Griceianly meaningful expression.
In my language, "brains in a vat" refers to brains in a vat.
My language is not Vatese; it is English
If I am a brain in a vat, my language is Vatese.
I am not a brain in a vat -- and neither are possibly you.
As Putnam pointed out, in order for a term to refer to an object we must
establish more than the mere existence of the object.
There has to be the appropriate causal relation between the word and
object, or we are back to claiming that in accidentally sneezing "Genghis
Khan",
Grice was referring to Genghis Khan.
But whether we accept this or attach stronger conditions to reference, it
is clear that any such move would make the given formulation of the
brain-in-the-vat thought experiment is invalid.
For then we would have:
My language disquotes.
In Vatese, "brains in a vat" does not refer to brains in a vat (via causal
constraint)
In my language "brain in a vat" is a Griceianly meaningful expression.
In my language, "brain in a vat" _pseudo-refers_ to brains in a vat (via
what Putnam calls "disquotation").
My language is not Vatese.
If I am a brain in a vat, my language is Vatese.
Therefore, I am not a brain in a vat.
The conclusion no longer follows, given the alleged ambiguity of "refers"
in the premises (even if 'refer' has only one sense). Grice speaks here of
AEQUI-vocation, rather, literally, 'same' voice.
If on the other hand we insist on a univocal sense of 'refer', either one
premise will contradict Putnams's disquotational principle, or we are not
entitled to appeal to the premises, insofar as they would beg the question
that we are speaking English, a language for which the disquotational
principle applies.
Consider:
I think that water is wet.
No brain in a vat can think that water is wet
--- Therefore, I am not a brain in a vat.
This main strategy is derived from Putnam’s Twin Earth argument.
Imagine a world that is indistinguishable from Earth except for one detail:
the odourless, drinkable liquid -- 'twater' -- that flows in the rivers
and oceans is composed of the chemicals XYZ and not H20.
If we take Oscar on Earth and his twin on Twin-earth, Putnam argues that
they would refer to two different substances and hence mean two different
things.
When Oscar utters,
"Pass me some water"
he refers to H20 and means water, but when Twin-Oscar says
"Pass me some water"
he refers to XYZ and thus means twin-water, or twater, in Twinglish, as
Putnam calls it.
If the meaning of 'water' and 'twater' are different, the concepts that
compose their beliefs should differ as well, in which case Oscar would
believe that water is wet whereas Twin-Oscar would believe that twater is
twet.
While Putnam’s original genial slogan was "Meanings just ain’t in the
head" (he meant his own head), the argument can be extended to beliefs as
well:
beliefs just ain’t in the head, but depend crucially on the layout of one’
s environment.
So it doesn’t seem possible that a brain in a vat could ever come to hold
a belief about water (unless he picked up the term from the mad-scientist's
use of 'water')
For better or worse, some philosophers -- including some Griceian ones,
claim that even if Putnam’s argument IS sound, it doesn’t do much to
dislodge Cartesian or global scepticism.
Cheers,
Speranza
Grice, H. P. Descartes on clear and distinct perception, in Studies in the
Way of Words.
Putnam, Hilary The Meaning of “Meaning.” Mind, Language and Reality:
Philosophical Papers, Vol 1. Cambridge: Cambridge University Press
Putnam, Hilary. Reason, Truth and History. Cambridge: Cambridge University
Press.
Putnam, Hilary. Reply to Wright. In P. Clark and B. Hale, eds. Reading
Putnam. Oxford, Blackwell.
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