This is the second email I just sent to Stevan Harnad. (See here for an explanation.)
Here is the rest of my response. It includes a response to earlier points about Descartes and skepticism, as well as a couple of points about categorization and definitions.
SH: "the category in question is color, not difference in color or shape."
I don't see a difference here. Categories are based upon differences. The category of "color" implies perceived differences in color, or else it is meaningless.
SH: “People no more need a definition of feeling than they need a definition of green.”
On the one hand, you say an ostensive definition is sufficient. On the other hand, you say that no definition is necessary. Isn't that inconsistent?
Some kind of definition is necessary. And people can define green. The category “green” is complemented by other colors. We can ostend green. You cannot provide an ostensive definition for what you mean by "feeling," however, because you claim to be talking about something with no complement. So you must opt for no definition at all. That makes your argument incoherent.
SH: “there is one fact – and one fact alone – of felt experience that is not open to skeptical doubt: that it is felt.”
I do not doubt the existence of feelings. But on what grounds can you assert that this is the only indubitable fact of experience?
SH: “Let me restate ['I am not thinking'] in the form that makes the contradiction more obvious.”
I think the contradiction is obvious enough, and replacing "thinking" with "feeling" doesn't make it more obvious to me.
I never said Descartes was wrong to think “I am not thinking” implies a contradiction. But it does not surprise us with a new kind of certainty; it only reminds us of a grammatical convention we already know.
SH: “what the method of doubt further reveals is that there is, surprisingly, a second kind of certainty, over and above logical necessity.”
The certainty of the cogito is grounded in logic, in the contradiction implicit in “I am not thinking (or feeling).” One might say, following Hintikka, that there is an existential inconsistency here in addition to the inferential one. Earlier I challenged this point, on the grounds that the "feeling" or experience of a contradiction is open to interpretation. That leaves us the cogito only with the certainty of logic, which is a matter of grammatical convention. So why claim there are two kinds of certainty here?
What is logical necessity, if not grammatical convention? What constitutes the necessity of truth—in mathematics or anywhere else—if not grammar?
Descartes experienced a contradiction when he thought “I am not thinking” because he was tied to his grammar. This does not make “I think” a necessary truth. It is contingent upon the grammar itself, and this may or may not be necessary. The question we might ask is, necessary for what? Or, to put it another way, how is a grammatical rule established as such?
Grammatical rules are established on the basis of their application. In what sense is an application of a grammatical rule necessary? Again, the question is: necessary for what?
SH: “No interpretational issues at all.”
I think this is demonstrably false. We can imagine plenty of scenarios in which the sentences “I do not feel anything” and “I am not thinking” are sensical, non-contradictory utterances.
A doctor asks, “Can you feel this?”
The patient replies, “No, I don’t feel anything.”
A wife says to her husband, “You’ve put on one red sock and one green sock!”
The husband replies, “I’m not thinking. My mind is somewhere else today.”
It takes an effort, however slight, to think of “I am not thinking” (or "I am not feeling") as involving a contradiction, and this act of intellection is just as subject to error as any other. This is not to say that the contradiction you are talking about is not there; it is only to say that seeing the contradiction amounts only to remembering a grammatical convention.
You accuse me of misunderstanding skepticism by confusing “truth” with “certainty.” I have made no such mistake. The issue here is what it means to doubt, and what it means to be certain. You can say that you are not certain that you have a body, but saying it does not amount to anything. It is a meaningless claim. Saying “this isn’t real” is similarly without meaning, unless it only means, “this isn’t what it appears to be.” But not-being-what-it-appears-to-
Following Wittgenstein, I do not view hyperbolic doubt as a viable means for establishing necessary truths. Epistemological foundations are constructed, not revealed. Grammars are necessary only with respect to particular ends and ways of living, and these may be adopted or criticized like anything else. Consider, for example, the critique of the ego made by Buddhists and some Western philosophers. Buddhists would not say “I am not thinking”; rather, they would say, “the I is an illusion.”I would not say the “I” is an illusion, exactly. Rather, I think it is a grammatical construction, something which exists as clearly as any other social, political, or cultural institution.
Earlier, I asked you to try an experiment which I think demonstrates the fact that the “I” is a grammatical construction. (Or, to put it in the language of feeling and avoid the personal pronoun, we can say the grammatical construction is the mysterious feeler which, you say, indubitably feels feelings.) The experiment: Try to observe yourself thinking or feeling something else. For example, try to locate yourself as an observer (or as a feeler) in your own observation of a table.
It is plain to me that all one observes is the table, and that any attempt to observe something else—an observer or feeler—requires language. There is a strong temptation to observe yourself by speaking to yourself, by saying, “I am looking at the table,” or something like that. I suggest that there is no observation of an “I” (or a “feeler”) outside of such utterances; and uttering “I exist” is not observing that one exists.Descartes was on to something. He believed that he existed as pure consciousness only so long as he was thinking. I would restate that as follows: The “I” exists only in so far as a particular grammatical convention is employed. The “I” comes into existence when it is thought, as Descartes said, but it only exists as a rule of language. It does not refer to anything beyond that language. (Similarly, democracy does not exist beyond the exercising of particular social conventions.)
For Descartes, the “I” had to be of a particular substance. For you, there is to be a mysterious, indubitable feeler. For me, these are just ways of speaking without specifiable extra-linguistic referents. We should not presume that, because grammatical conventions exist and have some use, that they must refer to anything that exists outside of that grammar, or that they reveal any non-grammatical truths.
I am not advocating global skepticism or nihilism. Rather, I am advocating practical limits on skepticism. I know I am thinking, because this is my way of life, and nothing more.