The Situation
1. Externalism places metaphysical conditions on having thoughts of a certain kind. Having a WATER-thought requires that I have water in my environment. It is also thought by some that since the truth of externalism is known a priori, then I can know a priori that if I am thinking that water is wet, then water exists in my environment.
2. On the other hand, it is thought that, given self-knowledge, I can know a priori that I am thinking that water is wet. (i.e. knowledge which makes no use of inference, evidence, or observation):Armed with (1) and (2) we get the following argument, which we will call Bog’s argument:
A. If I am thinking that water is wet, then water exists in my environment.This argument seems to be sound. If it is, however, it delivers a very strange (and unacceptable) result, assuming that we also accept assumptions (1) and (2) above. For this argument suggests that we can have a priori knowledge that water exists in our environment.
B. I am thinking that water is wet.
C. Water exists in my environment.
D-B-H Line (as summarized by Dorit)
I. If I am thinking that water is wet, then water exists. (I.e., externalism is true -- it lays down, as a condition on my having a WATER-thought that there be water in my environment.III flatly contradicts the conclusion of the first argument.
II. If I am thinking that water is wet, then I (can ) know “a priori” that I am thinking that water is wet. (I.e., privileged self-knowledge is possible.)
III. I can know (“a priori”) that I am thinking that water is wet, without knowing (let alone knowing a priori) that water exists in my environment. (This is because my knowledge of my thought’s content does not require knowing that I am satisfying the relevant conditions on having a thought with that content.
The situation, according to Dorit
“What I think this brings out is that the crucial step in Bog’s reasoning is provided by the claim that I know (A) a priori . . . So the question is: if the truth of externalism plus the posssibility of self-knowledge doesn’t entail the a priori knowability of the contents of my environment, why should accepting that I can know the truth of externalism “a priori” change the picture?
Presumably, it is my recognition or realization that (A) is true – that if I am thinking that water is wet, then there should be water in my environment - plus my concurrent recognition that right now I am thinking that water is wet that puts me in a position to deduce that there should be water in my environment.
But what I find problematic is this. If I am indeed to accept the DBH line, then at the same time as I affirm (so presumably believe) the truth of (A) I also know that my knowledge of the content of my thoughts in no way secures my knowledge of the existence in my environment of whatever actually gives my thought that content (i.e., of the thought’s ‘causal determiners’). Yet Bog would have us believe that my knowledge of externalism plus my self-knowledge should put me in a position to have a priori knowledge of the nature of my environment. So I submit that Bog’s argument must be inconsistent with genuine acceptance of the DBH line.
Accepting the DBH line means accepting that my (“a priori”) knowledge
of externalism plus my “a priori” knowledge of my thought’s content
does not after all imply that I can have a priori knowledge of the
existence of what fixes my thought’s content. Even as I know
what I am thinking – say, that water is wet, and even as I realize that
my thinking that thought requires the existence of water around,
I am not thereby in a position to ‘deduce’ that
water exists in my environs. I still need to check the world to ascertain
the latter claim. Indeed, if externalism is true, it may be part
of the requirement on my having the concept WATER that I recognize that
need!”
How I see the situation
First of all, the sentence “I am thinking that water is wet” seems to me to be ambiguous. It plays on a confusion between my seeming to have a WATER-thought that water is wet and my having a WATER-thought that water is wet. Let’s suppose that “I am thinking that water is wet” means:
a) I am having a WATER-thought that water is wet.So now the original Bog argument would go like this:
A. If I’m having a WATER-thought that water is wet, then water is in my environmentEven supposing that (A) is known a priori (because externalism is known a priori), (B) is not known a priori. Whether or not a person is having a WATER-thought depends on whether that person’s thought is about water, what the person says about his/her thought notwithstanding. If the argument were given using the personal pronoun ‘she’, such that (B) read, She’s having a WATER-thought that water is wet, all we would ask about are the conditions under which that is true of her, what she would say notwithstanding. I think the same holds true with respect to the above argument. All we need consider is (B’s) truth. If (B) is true, then it follows that water exists in my environment. However, if (B) is true, that is, if it is true that I’m having a water-thought, then given externalism, this couldn’t have been true without my a posteriori knowledge of what water is. Therefore, while (C) may follow, it does not follow that it is known a priori.
B. I’m having a WATER-thought that water is wet.
C. Therefore, water exists in my environment.
On the other hand, the sentence, “I am thinking that water is wet” may not mean that I am having a WATER-thought that water is wet. It might instead be read as saying something like I’m seeming to have a WATER- thought that water is wet. Following Descartes, this kind of seeming would be a kind of thinking, just as doubting is a kind of thinking. More importantly, you can have self-knowledge that you’re seeming to have a WATER-thought without there being water in your environment.
So now the original Bog argument would go like this:
1. If I’m seeming to have a WATER-thought that water is wet, then water exists in my environment.But now (1) is not known a priori. In fact, it is not even true. My seeming to have a WATER-thought that water is wet does not entail that water exists in my environment. So the argument is not sound.
2. I’m seeming to have a WATER-thought that water is wet.
3. Therefore, water exists in my environment.
Now here is the way I think that the original Bog argument generates confusion.
The first premise -- If I am thinking that water is wet, then water exists -- is read as saying, If I’m having a WATER-thought that water is wet, then water exists in my environment. (by Externalism). But then the second premise -- I am thinking that water is wet -- is not known a priori if we read it as saying, I am having a WATER-thought that water is wet. To assert this about yourself, assuming you accept that externalism is true, you have to know that water exists. I’m not saying that you cannot know this, but if you do, it would seem that you know it a posteriori. Therefore, the a priori reading we must use is, I’m seeming to have a WATER-thought that water is wet.
But nothing follows from the premises:
If I’m having a WATER-thought that water is wet, then water exists in my environment.and
I’m seeming to have a WATER-thought that water is wet.At least, not the conclusion that water exists in my environment.
Now this is the way I think we should see things. Given externalism, if I’m thinking that water is wet, then water exists. Suppose that we know this a priori. Knowing this (and accepting it), I should not assert anything about what kind of thoughts I’m having (as opposed to what kind of thoughts I seem to be having) if I don’t believe I know that water exists (or what it is). Now there are two cases to consider.
1) If I am thinking that water is wet, then water exists.First, let’s consider the case where the subject of ‘I’ believes s/he knows that water is wet, and therefore, asserts, I am thinking that water is wet (read as: I am having a WATER-thought). (3) will follow. However, though the person has self-knowledge (s/he is not using inference, evidence, or observation to know that s/he is having a WATER-thought), a requirement s/he has placed on him/herself for asserting self-knowledge claims of this type is that s/he knows that the external world supplies the thing s/he claims to have a thought about. In other words, if a person has accepted externalism, then this will constrain what s/he asserts that s/he claims to have self-knowledge about. The person will only assert “I am thinking that water is wet” after s/he thinks that a posteriori investigates justifies him/her making such a claim. So while (3) does follow, it is not known a priori. That is because the assertion of (2) requires a posteriori knowledge. But this does not mean that such a person cannot have self-knowledge that s/he’s thinking that water is wet (having a WATER-thought that water is wet). That is to say, that does not mean that the person does not have self-knowledge that she’s thinking that water is wet at the time she avows this.
2) I am thinking that water is wet.
3) Therefore, water exists.
But now suppose that someone accepts externalism (and believes s/he knows the truth of externalism a priori). Further suppose that this person believes that s/he knows that water exists and even that it is H2O. But let’s suppose that empirical investigation did get it wrong. The person is in a twater world, not a water world. Then what happens to the argument?
4) If I am thinking that water is wet, then water exists. (If I’m having a WATER-thought, then water exists).The person will assert (5), but the assertion that I am having a WATER-thought will be false. So modus ponens will not go through. But how about self-knowledge? Won’t the person be wrong about thinking that s/he is thinking that water is wet? (about having a WATER-thought -- as opposed to seeming to have a WATER-thought). Yes, that’s true. But the claim that we have self-knowledge does not state that we cannot be wrong about what we think we know. It is not a condition on self-knowledge that it be infallible.
5) I am thinking that water is wet.
6) Therefore, water exists.