I wrote this paper a little over a year ago and thought that it would be a good post for the blog. I hope y’all enjoy!

My aim in this paper is to construct the best argument for the skeptics’ conclusion that we cannot know anything be means of the senses, and then assess how one should view such an argument. I will first give the generic structure of a skeptical argument and then build an instance of this argument by using a specific skeptical hypothesis. I will then argue that although the argument seems plausible it seems less plausible then another argument that reaches a contrary conclusion. I will then give an argument on the skeptics’ behalf to make the skeptics strengthen what I believe is the weak premise in the argument. I conclude this paper with an assessment of this second argument and a brief assessment of what I think is going on in the debate between the skeptic and her opponent.

The skeptical arguments that I wish to focus on in this paper all have the same basic form. That is, they all start with the basic premise that if we are to know the truth of a proposition p then we must know that some skeptical hypothesis H is false. The skeptic will then go on to argue that we do not know that the skeptical hypothesis H is false, and because of this we do not know that p. The type of skeptic that I wish to engage is the skeptic who argues that we cannot come to know anything by means of our senses. So, for p let us substitute that we know things through our sense experience. As for H it seems that any of the major skeptical hypotheses would work to get the argument to work. Take the brain in a vat hypothesis. The brain in a vat hypothesis claims that it is possible that all of my experiences are not real representations of the outside world and in actuality I am just a brain in a vat getting fed artificial sense experiences by some sort of mad scientist. Clearly if this hypothesis is true I cannot know anything by means of my senses, since they are artificial and do not truly represent the outside world.

Using this as our skeptical hypothesis we can now build an argument that we cannot know anything through our senses. The argument goes as such:

(1)  If I am to know anything by means of the senses then I must know that I am not a brain in a vat.

(2)  But, I do not know that I am not a bran in a vat

(3)  Therefore, I do not know anything by means of the senses.

At first glance this argument seems to be very intuitively plausible. The first premise definitely seems to be true, and actually follows from the closure principle about knowledge. The closure principle is that for any conditional statement, if a, then b if someone knows that if a then b, then they are in a position if they know that a to know that b. As I said, it definitely seems that if we are brains in vats then there is no way that we would be able to know anything through the sense. And, if this is true then so is its contrapositive, which is just the first premise of the argument.

What about the second premise? There seems to be some sort of intuitive pull to the idea that I do not know whether or not I am a brain in a vat. How would I be able to know that it is the case that I was not a brain in a vat? The experiences I would have would be qualitatively the same. So, how could I tell the difference? But, still it is not clear that just this metaphysical possibility is enough of a motivation for me to accept the this premise of the argument. Surely, there is a possible world in which I am a brain in a vat, but this doesn’t mean that I should believe that for all I know I could be a brain in a vat. So, it seems that this premise would be in need of some further reasons in order to make this argument seem persuasive. Further, it also seems that due to this premise there is something a little fishy going on in the argument. This premise is a skeptical premise that takes us to a skeptical conclusion. One may feel that there is an air of question begging going on because of this, the argument should not take us from skeptical premises to a skeptical conclusion but instead, it should be an argument that just takes us straight to skepticism without making any skeptical assumptions. G. E. Moore responds to such arguments by claiming that we should be more confident that the skeptical conclusion is false then in the fact that we are brains in vats. So, a counter argument to the skeptics’ argument can be made like so:

(4)  If I am to know anything by means of the senses then I must know that I am not a brain in a vat.

(5)  I do know things by means of the senses (for example: that I have hands).

(6)  Therefore, I know that I am not a brain in a vat.

The argument itself does beg the question against the skeptic, since (5) is just the denial of what the skeptic wishes to conclude, which does not make this argument entirely satisfying. But, I am sympathetic to what is going on here. It seems that given just the basic argument that I have presented so far there is not a truly compelling reason to accept the conclusion of the skeptics’ argument because of premise (2). I agree with Moore in thinking that we ought to be more confident in believing (5) then (2), especially if we are not given any sort of compelling argument to accept (2).

So, from here the question is, can the skeptic give any further justification for (2) that will make the skeptical argument more compelling? In Pryor’s paper “The Skeptic and the Dogmatist” he makes an argument for skepticism, which he thinks is more compelling than the argument that I have offered at the beginning of this paper. Really it seems to me that what this argument does is offer us more compelling reasons to think (2), instead of just considering the possibility itself of us being brains in vats. So, I will just use it as a supplementary argument to the one I offered at the beginning of this paper.

Pryor uses the evil demon as the skeptical hypothesis, but I will continue just to use the brain in a vat hypothesis to stay consistent with the rest of this paper. The argument will go like this:

(7)  If I am to know that we are not a brain in a vat, then we must come to this knowledge through the senses.

(8)  But if I am to know anything through the senses then I must already know that I am not a brain in a vat.

(9)  Therefore, I do not know that I am not a brain in a vat.

(7) seems as if it should not be very contentious, it is hard to imagine how someone could be successful showing only on a priori considerations that they are not a brain in a vat, and it is hard to think of any compelling methodological reasons to reject this claim either, so I think that we should grant the skeptic that in order for us to know that

(8) definitely seems to have some intuitive pull to it. It seems that if I were to come to know anything through the senses then I must have already ruled out (prior to my coming to know things through the senses) that I am not a brain in a vat. Really all this is, is a repeat of (1), with an emphasis on the priority of ruling out the brain in a vat hypothesis prior to gaining any sort of knowledge through sensory experience.

I have already granted that the first premise seems to be a relatively strong one, and should not be considered a point of contention. So, this means that if one were to argue against the skeptic in anyway (8) would have to be the premise to deny. This is what Pryor ends up doing in his paper. Pryor argues for a position called dogmatism in where (8) is rejected on the grounds that we do not need any antecedent reason to rule out the skeptical hypothesis to be justified or know that we can have knowledge through the senses. Pryor says:

“You could have this justification even if there were nothing else you could appeal to as ampliative, non-question-begging, evidence that p is the case. Hence, to be justified in believing p, you do not need to have the antecedent justification the skeptic demands. You do not need to have the evidence to rule the skeptic’s scenarios out, in a non-question-begging way.” (532)

To me this view response seems to be correct. It seems like an awfully high requirement for the skeptic to ask of a person to be able to rule out their hypothesis prior to them being justified or being able to have knowledge of things through sense experience. This is where I think the skeptic goes wrong. She demands too much work for us to be able to come to have knowledge (or justification) in something that it seems we should not be required to have to do so much work for. The intuition that I am trying to pull at here is that our knowledge of the world that we have immediately through the senses should be easy, it should not require for us to go through and disprove or argue against some skeptical hypothesis for us to have that sort of knowledge.

So, what is going on here? Why do the skeptical arguments seem to be so intuitively plausible? Well I think the reason for this is that when we consider these arguments we have a natural inclination to conflate two different concepts, the first being our knowledge of the world and the second being our confidence in our knowledge of the world, or, alternatively, we conflate knowledge with certainty. I think that when we think of knowledge since it is factive, which makes it an absolute notion I think that we take this beyond what we should and think that this means that we must have no possible way in which our knowledge could be rendered false. But, as I said earlier about the skeptical arguments this too seems to be too strong of a requirement for knowledge. Though we are naturally inclined to want certainty for our knowledge our knowledge of the world does not require certainty of our beliefs.

In conclusion I have given what I believe to be the best argument for the skeptical conclusion and given what I think is the correct reply to this argument. I then gave an assessment of why though the skeptical argument is wrong, we find it to be very plausible.

Post by Cruz Davis


1 Comment

  1. ‘Surely, there is a possible world in which I am a brain in a vat, but this doesn’t mean that I should believe that for all I know I could be a brain in a vat.’

    This seems contradictory. If we believe that there is a possible world in which we are BiVs, and we accept that in that world we would have qualitatively identical experiences as we do in this world, then it seems that we already believe that for all we know, we are brains in vats.

    Ultimately, I think the word ‘knowledge’ here might be unsuited for this. I think we agree that we cannot have certainty that we aren’t BiVs. I agree that we aren’t justified (at least according to anything I’ve heard argued) in believing that we are BiVs.

    By knowledge, do you mean true justified belief?

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