Skeptical
arguments challenge even the very solid pieces of our knowledge. Take, for
example, your belief that you have hands. You see your hands, you hold and move
things with them. So, what can possibly threaten your knowledge or true belief
that you have hands?
In this
essay, I shall argue three responses to skepticism based on the brain-in-a-vat
(BIV) hypothesis and conclude that despite their validity and plausibility,
they fall behind skepticism to constitute as satisfactory alternatives.
The skeptical argument can be
constructed as follows:
(1)
I
don’t know that I’m not a BIV.
(2)
If
I don’t know that I’m not a BIV, then I don’t know that I have hands.
(3)
I
don’t know that I have hands.
This argument is indeed a valid argument in the sense that (1) and
(2) are plausible premises and (3) logically
follows from these premises. Regardless of how farfetched or against
commonsense may it seem to assume that you are a brain-in-a-vat, you still
don’t know you are not one. And this very fact is what underlies the strength
of skeptic’s argument: It is straightforward and its premises are difficult to
rule out or there is a possibility that they are true or at the very least we
don’t know that they are false. Hence, any argument developed against
skepticism must question the soundness of
the argument.
In response to BIV argument, G. E. Moore states that
the conclusion of BIV argument is less plausible than its premises and thus reconstructs
the BIV argument (counter-BIV argument) by asserting the opposite of the
skeptic’s conclusion:
(1)
I know that I have hands.
(2)
If
I don’t know that I’m not a BIV, then I don’t know that I have hands.
(3)
I know that I’m not a BIV.
What Moore suggests is that in the face of two
conflicting premises, we should opt for the common-sense premise that we know we have hands, which entails the
conclusion that we know we are not
BIVs.
Though Moorean argument is valid, it is still not a
satisfactory alternative to skepticism. First, it does not explain how Moore knows that he has hands. The skeptic who
asserts that he doesn’t know whether there is an external world might easily
claim that he does not know that he
has hands. He might as well be dreaming that he has hands. Second, the premises
of Moorean argument remain insufficient in convincing the skeptic who would not
agree with its conclusion. And finally, the skeptic might allege that Moorean
premises lack proof in order to constitute as ‘knowledge’.
Another response to skepticism is argued by “Relevant Alternatives” theory, which
basically says that “the main ingredient that must be added to true belief to
make knowledge is that one be in a position to rule out all the relevant alternatives to what one believes”
(DeRose, 1999, p. 14). What underlies the BIV argument is that since we cannot
discriminate between our actually having hands and not being a BIV, we don’t
know that we have hands. According to the relevant alternative theorist, this
discrimination is not relevant anymore because our being a BIV is not a relevant alternative to our having hands.
Thus, we can deduce that we know we have hands.
Accordingly,
the BIV argument can be constructed as follows:
(1)
You know you have hands.
(2)
You know that your having hands
entails your not being a BIV.
(3)
You don’t know that you are not a
BIV.
This argument rejects the second premise of BIV
argument and asserts that you know you have hands though you don’t know you are
not a BIV. This, in turn, implies that this theory denies the “Closure Principle”,
which basically says that if S knows p,
and p entails q; then S knows q. Hence, the main concern that can be raised
by a skeptic against relevant alternatives theory is its denial of this intuitively
appealing principle. Another important problem for this approach is the lack of
a principled basis for what constitutes relevant and irrelevant alternatives.
The contextualist response to BIV argument deploys a
different approach and focuses on the use of the word “know” in differing contexts. The utterance of “I know” can be ascribed freely to knowledge in low-standard
settings, but cannot be done so liberally in high-standard settings. One can
ask what the point is epistemologically in distinguishing between high and
low-standard settings? The point is that the skeptical argument creates such a
context that we count no more as “knowers” even when we utter such a
straightforward sentence as “I know I
have hands”. The skeptic’s demanding high standards raise questions such as
“how do I know my having hands?”, “How do I know that I’m not a BIV who has the
same sensory experiences as a human-being?” On the other hand, in a
non-philosophical sense, I ordinarily do
know that I have hands and cannot be deemed false in claiming so. Since contextualism
employs two types of contexts, it resolves this seemingly paradox and truth-condition holds in both settings.
Thus, contextualism is a plausible argument and preserves
the “Closure Principle”, which holds in both high and low-standard settings:
a.
If the meaning of “know” is set by low
standards, I know that I have hands
and I know that I’m not a BIV.
b. If the meaning of “know” is set by high
standards, I don’t know that I have
hands and I don’t know that I’m not a
BIV.
The main criticism against contextualism is that since
high-standard settings allow the use of skeptic’s argument asserting “I don’t know”, it makes considerable
concessions to skepticism. Another objection is that people are not strictly
context-sensitive, which implies that the way they use the word “know” is not determined at all times. Besides, the way contextualism assumes
strict context-sensitivity ignores people’s intention
when they utter the word “know”.
In summary, skeptical argument seems to enjoy a higher
degree of plausibility and soundness in comparison to responses raised against
it. The strength of the argument mainly stems from the fact that the skeptical
hypothesis is such that “…we cannot rule
out her hypothesis, that it’s possible that her hypothesis is true, or that we
don’t know that her hypothesis is false.” (DeRose, 1999, p. 2)
BIBLIOGRAPHY
DeRose,
Keith (1999), ‘Responding to Skepticism’, Oxford
University Press.
