Wednesday, June 24, 2009

Wallace Reread

Summer Wednesdays here at Brain Hammer will be dedicated to reflections on David Foster Wallace’s (DFW’s) Infinite Jest (IJ) and other works as I participate in the Infinite Summer project to plow through IJ at a pace of 75 pp a week til Sept 22. (Brag: I’ve already read IJ once. I’ve also read like a million other things by DFW, including Everything and More.) In doing so, I’ll be (somewhat) emulating a blogger who shall remain unnamed so that she doesn’t have to kill me when I come home tonight. I have a vague ambition to bring a professional philosopher’s point of view to the whole endeavor, but it occurs to me that this all might just veer toward the random. Like this:

Random thought #1. I was killing time in a B&N the other day and flipping through This Is Water, the bound version of that commencement speech DFW gave not long ago. The jacket flap calls him a philosopher, and though I get a bit cringe-y about who the popular media call a philosopher, in this case I don’t mind so much. I got to take a peek at DFW’s undergrad philosophy thesis a while ago and it was pretty damn impressive. He mastered way more modal logic mojo than I ever did as an undergrad. (Probably totally irrelevant autobiographical detail: DFW’s dad, James Wallace, was a philosophy prof at U of I Urbana while I was an undergrad in the early 90’s. I retrospectively regret not having taken a class from him. It somehow also seems relevant that I regret blowing an opportunity to take a class from William Gass when I was in grad school at Wash. U. in the late 90’s.) It’s well known that DFW gave some serious thought to pursuing a career in philosophy. It also seems clear that we’re all better off that he didn’t. (Dogmatic assertion: no piece of 20th/21st century analytic metaphysics could be possibly be more valuable to humanity than Infinite Jest.) But what remains unclear, though we’ll see as we go, is how much he contributed to philosophy anyway.

Random thought #2. One thing I’m very interested in about IJ and other DFW writings is this. In an interview I don’t have at hand just now, DFW described a buzz that he got when he wrote, a buzz, if I recall correctly, he admits feeling addicted to. Under the right conditions, the intellect can be a joy unto itself. This is a very seductive idea, especially to a consumer and producer of ideas. DFW was also aware, of course, of a dark side to this process. One thing I recall DFW saying (paraphrase from memory coming up) in This is Water, though I forget to whom he attributes it, is this: The mind makes a terrible master.

Random thought #3. I feel that I don’t fully grasp why, when republishing that story about the kid with the spiders in Oblivion, DFW re-titled it, Philosophy and the Mirror of Nature. People that want to drop by and school me on this one are more than welcome. Invoking Rorty seems appropriate to the "better novels than metaphysics" theme, but surely that can't be all there is to it.

Tuesday, June 23, 2009

Chomsky has no patience for externalism whatsoever

It's amusing watching the video below and seeing the philosopher (Peter Ludlow) totally fail to get the scientist (Noam Chomsky) concede that there's anything at all that needs to be taken seriously about externalism.

See also:
The Varieties of Externalism

Are there any non-question-begging arguments for externalism?

Friday, June 19, 2009

Swamp Draft Online

Thanks, all of you who read and commented on the serialization of my new Swamp Mary draft. Here it is as a single pdf: "Swamp Mary Semantics: A Case for Physicalism Without Gaps"

Wednesday, June 17, 2009

Phenomenal Knowledge is Abeyant, Not Occurrent

Another possible source of the intuitiveness of the Experience Requirement is that it arises when we compare the relatively sparse information content of occurrent thought to occurrent visual experience. Occurrent thought arguably is limited by the capacity of working memory, and it is well known that working memory constitutes a comparative bottleneck in the large context of human information processing (Sperling, 1960). Could this disparity between thought and experience (in terms of, for instance, complexity or informational content) even serve as a basis for the truth of the Experience Requirement? DeLancey (2007) and Schier (2008) have pursued defenses similar to the one just suggested.

(Both DeLancey and Schier seek to lend support (consistent with physicalism) to the intuition that Mary learns something upon seeing red. Central to both of their cases are comparisons between, on the one hand, visual experience, and, on the other hand, scientific theoretical understanding. DeLancey suggests that scientific understanding has a relatively low informational content (measured as Kolmogorov complexity). Schier suggests that scientific understanding is relatively impoverished for being, in her words, “fragmented.” It seems, however, from various examples discussed by both authors, that they are comparing visual experiences to the wrong sorts of mental entities: relatively impoverished occurrent states of working memory or language processing instead of vastly more capacious states of standing knowledge.)

However, I think that such a line of thought is ultimately mistaken. The mistake arises in treating phenomenal knowledge as a kind of occurrent thought. Phenomenal knowledge, like knowledge generally, is abeyant or standing. This fact about phenomenal knowledge is what allows us to retain our knowledge even under general anesthesia when we, presumably, have no occurrent mental states. Our standing conceptual knowledge, as argued above, is, from an information-theoretic point of view, enormously capacious, and more than adequate to the task of capturing the content of visual experience.

While it is mistaken to draw conclusions about what Mary can know from comparisons of occurrent thought and experience, if such mistaken experiences are widespread, then this fact can help to explain the widespread intuitiveness of the Experience Requirement. If, on the other hand, such comparisons are not widespread, we still have the previously discussed explanation at our disposal. People are drawn to the Experience Requirement because of a relatively rough grasp they have of the enormous bandwidth difference between vision and the other sensory modalities.

Concluding “Swamp Mary Semantics”

In this paper I have assumed physicalism and argued against gappy physicalism. The basis of my complaint is that, if it is possible for a Swamp Mary to have knowledge of phenomenal redness without herself having experienced red, then gappy physicalists have to supply an explanation of why it is that prerelease Mary would be phenomenally ignorant. I have argued further that, upon examining the various psychosemantic strategies for accounting for Swamp Mary’s knowledge, there is no basis for also maintaining prerelease Mary’s ignorance. Gappy physicalist may want to contemplate responding to my arguments by denying the possibility of Swamp Mary, but I am aware of no principled basis available for them to do so. I have offered that physicalists are better off just abandoning the intuition that prerelease Mary is phenomenally ignorant. In the service of making such an abandonment strategy more palatable, I have offered considerations designed to show why the key intuition behind the Mary thought experiment may have seemed plausible while nonetheless being false.

Previous posts:

1. Swamp Mary Semantics: A Case for Physicalism Without Gaps

2. There’s Something About Swamp Mary

3. Putting the Physicalism in Gappy Physicalism

4. Swamp Mary and the Psychosemantic Challenge

5. Nomological Psychosemantics in the Swamp

6. Descriptive Psychosemantics and Phenomenal Knowledge

7. Can the appearance of a phenomenal-physical gap be explained away?

8. Bandwidth and Storage in the Human Biocomputer

Wednesday, June 10, 2009

Bandwidth and Storage in the Human Biocomputer

One ballpark estimate of the memory capacity of the human brain is that it is in the range of 10^13 - 10^17 bits (Tipler, 1995). These numbers are much too large for current purposes if we assume that not all of the brain’s memory is in the service of concepts. A smaller number may be arrived at by assuming that concepts are restricted to pre-frontal cortex (PFC). The volume percentage of PFC to the whole brain is 12.51 (McBride, Arnold, & Gur, 1999) and thus we arrive at a reduced memory capacity estimate in the ballpark of 10^12 bits.

Is what Mary knows while staring at red for the first time simply too much information than can be squeezed into a memory store of 10^12 bits? It seems not.

An early estimate of the bandwidth of the human eye for color vision is 4.32 x 10^7 bits/sec (Jacobson, 1950, 1951). A more recent estimate is 10^6 bits/sec (Koch et al., 2006) aka a megabyte per second (1MB/sec). The computer-savvy reader may already have an intuitive grasp of 1MB/sec. The Wikipedia entry for “megabyte” (accessed July 24, 2008) tells us that a megabyte of data is roughly equivalent to a 1024x1024 pixel bitmap image with 256 colors (8 bpp color depth), 1 minute of 128 kbit/s MP3 compressed music, or a typical book volume in text format (500 pages × 2000 characters).

Assuming Mary has to stare at a red object for a full second to know what it’s like to see red, our lowest estimate of human memory capacity is still an order of magnitude higher than what comes into her eye during that second. (And that’s assuming that Mary has a normal-sized human PFC. Physically omniscient Mary may likely have a bigger brain than normal.) From a purely information-theoretic perspective, giving her bigger lobes would make it even easier to know what it’s like.

So, from an information-theoretic perspective, Mary’s memory capacity is easily large enough for phenomenal knowledge to be conceptual. But the information has to get in there somehow and maybe color vision is the only pipeline fat enough to do the trick. Unfortunately for the defender of the Experience Requirement, there’s no purely information theoretic basis for her position.

Jacobson (1950, 1951) gives a bandwidth estimate of 4.32 x 10^6 bits/sec for the eye for black and white vision and an estimate of 9,900 bits/sec for the bandwidth of the human ear. Continuing with our assumption that Mary would require a full second to gain, via color vision, knowledge of what it’s like to see red, then the very same amount of information can be acquired by a color blind person in 10 seconds and a blind person acquiring the information auditorially would need a full 73 minutes. Reducing our estimate of how long Mary needs to a tenth of a second means that the color blind could acquire that information in about a second and the fully blind in seven minutes.

(Of course, none of this is to say that, for example, the blind person would be hearing red. But it is to say that she is learning whatever is to be learned by the sighted when they see red. The information acquired about red may enter sensory systems without giving rise to conscious experience.)

The above considerations about bandwidth help us to see why the Experience Requirement may strike so many people as plausible. There is a marked difference between what you can learn in a second and what you can learn in 73 minutes. And it is reasonable to assume that people have an at least rough grasp of the informational capacities of their various sensory systems.

Nonetheless, regardless of whether we interpret Hume’s assertion about what the blind can know about color as a claim about nomological, metaphysical, or logical possibility, the claim receives no support from these information-theoretic considerations. From the information-theoretic perspective it is nowhere near impossible for the blind to acquire information of the presence of redness. They just need a longer time than the sighted to do so.

Monday, June 8, 2009

Can the appearance of a phenomenal-physical gap be explained away?

In the remaining posts of this series I address a question that I think is not addressed frequently enough in the literature. Why do people suppose that there is an epistemic gap? Asked in the context of discussions of Mary, the relevant question to ask is: Why do people suppose that prerelease Mary is phenomenally ignorant?

It is no answer to such a question to say that it is intuitive that prerelease Mary doesn’t know what it’s like to see red. For the next question to raise is: Why is that intuitive? And it is no answer to that question to credit the intuition as being true. The truth of an intuition can’t suffice to explain its intuitiveness. Further, if the above arguments concerning Swamp Mary are sound, the intuition in question is false. I think that in general, if an intuition retains its intuitive pull despite being shown to be false, it helps to have an explanation of the source of the intuitive pull. It is toward such an explanation that the current section is directed.

The intuition under question is a thesis that I will, following an earlier work (P. Mandik, in press),  call the Experience Requirement, “the thesis that, for some experiences at least, and red experiences in particular, knowledge of what it’s like to have such an experience requires that the knower has had or is currently having such an experience.”

In an earlier time, classical empiricism was the grounds for a defense of the Experience Requirement. We see expressions of something very close to the Experience Requirement in the work of Locke and Hume. Here’s Locke from An Essay Concerning Human Understanding : “…we see nobody gets the relish of a pineapple, till he goes to the Indies, where it is, and tastes it.” Here’s Hume from An Enquiry Concerning Human Understanding: “A blind man can form no notion of colours; a deaf man of sounds. ….A Laplander or Negro has no notion of the relish of wine.” Locke and Hume offer the Experience Requirement as a piece of common sense that is supposed to help build their case for their theory of ideas. The thought seems to be that their empiricistic theory of ideas is supported by how well it is able to explain the Experience Requirement: if ideas are made of sensory impressions or copies thereof, then of course “a blind man can form no notion of colour.” 

I have serious doubts about whether the account whereby concepts are composed of sensory impressions or copies thereof will stand up to neuroscientific scrutiny. Though I think Weiskopf (2007) makes a convincing case against the neurophysiological plausibility of this kind of concept empiricism, I will not recount the case or pursue this line further here. Instead, I present considerations that directly target the Experience Requirement. 

One way of formulating a question about the truth of the Experience Requirement is as follows. Is it possible that the informational channels that put normally sighted persons in contact with redness are more capacious than either any other sensory input channels or the human memory systems that constitute our objective conceptual grasp of our inner and outer worlds? When we look to scientific estimates concerning, for example, the bandwidth of human color vision, we find the basis for the following two lines of thought. The first is that we can explain why people may have found the Experience Requirement plausible. The second is that considerations concerning neural bandwidth and storage do not suffice to ground the Experience Requirement’s truth. I develop these lines of thought further in the next post of the series.

Friday, June 5, 2009

Descriptive Psychosemantics and Phenomenal Knowledge

I have previously argued that gappy physicalists who embrace Swamp Mary cannot account for her satisfaction of psychosemantic criteria along the lines of either quotational, causal, or nomological accounts.

            Let us turn, then, to examine the availability, or lack thereof, to gappy physicalists of a psychosemantics along the lines of Descriptive-isomorphism. It helps to first begin by examining a clear case to which Descriptive-isomorphism is most likely to apply. Suppose that someone, let us call him George, is an otherwise normal human who has never before seen the Japanese flag. Let us suppose that George has normal color vision, and has had a typical range of color experiences including having seen red and white before. Suppose further that George has seen various shapes before, including circles and rectangles. George just has never seen a Japanese flag before. Without showing him one, how can we augment his knowledge to include knowledge of what it would be like to see one? Here the answer seems quite simple. We convey to George a description along the lines of “red circle centered on a white rectangular background.” The adequacy of such a description, according to Descriptive-isomorphism is due chiefly, if not exclusively,  to two factors. The first factor is the flag’s being a structured complex (with the comparative simples being redness, circularity, etc. and structural relations being the having of redness by the circle, the centering of the circle on the rectangle, etc.). The second factor is the description’s being a structured complex allowing it to pick out the parts of the complex and their structural relations to each other. It may perhaps ease subsequent exposition to label these two factors “content complexity” and “vehicle complexity,” respectively.

            Given how Descriptive-isomorphism works for George, it is quite difficult to see why it wouldn’t work just as well for Mary. One of the key suppositions of physicalism is that qualia are ontological complexes of non-phenomenal relative-simples. Thus are qualia in a position to satisfy the first key factor of Descriptive-isomorphism, the content complexity factor.  And Mary is physically omniscient, so there would be no non-phenomenal entity or non-phenomenal relations between entities that would exceed her grasp. Thus are states of Mary in a position to satisfy the second key factor of Descriptive-isomorphism, the vehicle complexity factor. I am aware of no third factor essential to Descriptive-isomorphism, so I’m aware of no basis for the gappy physicalist to embrace Descriptive-isomorphism as the psychosemantics of Swamp Mary’s phenomenal knowledge while maintaining prerelease Mary’s phenomenal ignorance. 

            It’s natural here for the gappy physicalist to try to claim that Mary cannot actually satisfy the vehicle complexity factor of Descriptive-isomorphism. The maneuver I have in mind is to affirm that while Mary is able to represent the phenomenal facts under one description, there is some other description that prerelease Mary is not able to represent the facts under. One way in which this might be put is to say that prerelease Mary knows the facts under a physical description but not under a phenomenal description. It is hard to see, however, what is to distinguish kinds of description here in a way that is also going to be consistent with key tenets of both Descriptive-isomorphism and gappy physicalism.

            Suppose that the relevant difference between the descriptions is thought of as analogous to differences between inter-translatable descriptions from distinct languages. Compare the difference between, for example, the English phrase “white rectangle” and the Pig Latin phrase “itewhay ectangleray”. According to Descriptive-isomorphism, their inter-translatability is due to structural commonalities between the descriptions (or commonalties between structures such as languages or language games that the descriptions are respectively embedded in). What makes them different descriptions isn’t going to be any difference in what they are descriptions of, that is, differences in semantic content, but instead differences in the representational vehicles. (The vehicular differences may, of course, be relational as well as intrinsic.)

How can such vehicular differences suffice for prerelease Mary’s phenomenal ignorance? The suggestion along such lines has to be something like that Mary may be able to get into one kind of state, but not be able to get into another. But note now what the key features of this account of Mary’s prerelease omniscience and ignorance amounts to: her omniscience is due to her having a representation, under some description, of every fact, and her ignorance is due to there being states that she is nonetheless unable to get into. But this is just to give a version of the ability response(Lewis, 1990). And the ability response is a defense of physicalism that is not a gappy physicalism. It is crucial to gappy physicalism to hold that what Mary lacks prerelease is a kind of knowing-that, as opposed to a kind of knowing-how.