Thursday, September 3, 2009

Bertrand Russell: Leaping Tall Proofs in a Single Bound Variable

Back when I was a human larva, Bertrand Russell was one of the first philosophers I ever discovered, let alone read in any depth. I was raised moderately Catholic, but by the time I was 11 or 12, I was wrestling with nascent feelins that Catholicism--and indeed, all of religion--might be terribly inadequate. One day, while hanging out in a bookstore (yeah, I was that kind of 12 year old), I happened on a book called Why I'm Not a Christian. I read the titular essay right then and there and, after buying the book, soon devoured the rest of them. Russell's clear, lucid, humorous prose expressed all the doubts I'd been unable to put into words (and then some!) and exposed me to serious philosophy for the first time. I was hooked, and before long I was plowing through Wittgenstein's Philosophical Investigations and every other piece of philosophy I could get my hands on. Though I'm not a logician--and though Russell's work on religion was only a very, very small part of his mostly logic-oriented corpus--I still have a soft-spot in my heart for him: he was my first doorway into what eventually would become a career.

That's why I'm so delighted to discover that two gentlemen (one of them a computer science professor at Berkeley!) are publishing a graphic novel--that's what you call you comic book if you want it to be taken seriously--about Russell's struggles with life, mathematics, philosophy, and his own tenuous sanity. Snip from the article about it in The Independent:

Through GE Moore at Cambridge, he discovered Leibniz and Boole, and became a logician. Through Alfred Whitehead's influence, he travelled to Europe and met Gottlob Frege, who believed in a wholly logical language (and was borderline insane) and Georg Cantor, the inventor of "set theory" (who was locked up in an asylum) and a mass of French and German mathematicians in varying stages of mental disarray. Back home he and Whitehead wrestled with their co-authored Principles of Mathematics for years, endlessly disputing the foundations of their every intellectual certainty, constantly harassed by Russell's brilliant pupil Wittgenstein.

If the subject matter seems a little arid, with its theories of types, paradoxes and abstruse language (calculus ratiocinator?), and if its recurring theme of how logic and madness are psychologically intertwined seems a touch gloomy, don't let that put you off. Logicomix tells its saga of human argumentation with such drama and vivid colour that it leaves the graphic novel 300 (Frank Miller's take on the Battle of Thermopylae) looking like something from Eagle Annual.

This sounds great--something like Wittgenstein's Poker with pictures. It looks like the book itself isn't available for preorder on Amazon (it's going to be released in Europe on September 7, and sometime after that in the United States), but you can sign up to be notified when it is available. This is certainly something that I'll be making room in my schedule to read!

Sunday, August 9, 2009

Quicklink: Ben Bradley and Roy Sorensen on Death

I've been thinking a lot about death lately--there's no particular reason, I just find some of the questions surrounding the philosophy of death fascinating. Perhaps primarily, I'm intrigued by the intuition that some people (apparently) have that either (1) death is not an evil--that is, it isn't something that we should fear for ourselves--or that (2) indefinite life isn't something to be desired. I suspect that both of these intuitions come to more or less the same thing, but they don't seem to be universally correlated: some people will hold (1) without holding (2). When I first started talking to friends and colleagues about this issue, I was rather shocked to find out that anyone holds (1) or (2) at all--they seem so obviously false to me that I have a hard time fathoming how anyone could hold them. Still, apparently this issue is non-controversial; I've got a paper floating around in my head attacking (1) and (2), but until it manifests (maybe later this semester?), I'll have to settle for just pondering. In the mean time, here are Ben Bradley (Syracuse University) and Roy Sorensen (Washington University-Saint Louis) discussing some of these issues. The discussion is a little slow (and Ben Bradley is--ugh--a hedonist), but BloggingHeads lets you watch the whole thing at 1.4x speed. I recommend that option. They touch on some of the fundamental questions in the field, including (1) and (2)--Roy Sorensen and Ben Bradley both seem to share my shock about the fact that someone might hold (2). Enjoy!

Thanks, Leiter!

Wednesday, July 29, 2009

Having Your Qualia and Eating Your Physics Too

Can we coherently acknowledge the existence of qualia without being forced into a non-physicalist stance about the contents of the world? I'm back at CTY--as I am every summer--and today our philosophy of mind class got to Jackson's "Epiphenomenal Qualia." I was somewhat surprised, having not read the article since last year, to find that my own views on it seem to have changed considerably. Specifically, while I still agree with the main thrust of Jackson's argument (that is, that qualia exist), I'm much less impressed with the quality of his argumentation and the route by which he arrives at his conclusion; more specifically still, I'm incredibly skeptical that his "what Mary didn't know" argument shows anything like what it is purported to show. Qualia certainly deserve to be included in our ontology, but that emphatically doesn't imply that we ought to reject the physicalist picture of the world. Let me try and show how I think these two statements can be reconciled.

First, I suppose a bit of background is in order. Readers may already be somewhat familiar with the Mary case--Jackson's version of the knowledge argument against physicalism--so I won't waste a whole lot of time detailing the moves. Still, it's worth laying out exactly how the argument is supposed to proceed; as we shall see, the precise wording of one of the premises can make all the difference between soundness and total incoherence. Let's start with the informal presentation. Briefly, the standard presentation goes something like this.

Mary is a gifted neuroscientist who has dedicated her life to studying human color perception. She's learned everything there is to know about the physical process of seeing color: she knows everything about how the surface spectral reflectance of various objects interacts with environmental variables to produce changes in the photoreceptors of the eye, how those changes produce neural excitations, how those excitations are processed in the brain, and so on. She knows all the physical facts about how humans perceive color. Somewhat ironically, Mary herself has never perceived color. Her eyes (say) have been surgically altered so that she is only able to view the world in shades of grey. Nevertheless, her studies have proceeded beautifully, and she is now in a position of perfect physical knowledge. With this complete knowledge in hand, Mary undergoes an operation to reverse her perceptual idiosyncrasy; the procedure to keep her from being able to see color is reversed, and Mary's biology is returned to normal. When Mary awakens from the operation, she is presented with a red rose, and actually sees red for the first time. Does Mary learn something new?

On the standard interpretation, we're now presented with two horns of a dilemma: we're either forced to say that no, Mary has learned nothing new when she first sees color--an ostensibly counter-intuitive position to hold--or we're forced to say that yes, Mary learns something new when she sees the rose. If we take this second horn, though (so the argument goes), we must also admit that there are facts about color experience that are not physical; after all, ex hypothesi Mary knows all the physical facts about color vision--if she learns something new by actually seeing color, that new fact must be a non-physical fact. Therefore, the physicalist picture of the world is, while perhaps not strictly false, incomplete in an important way: it is incapable of accounting for the qualitative character of conscious experience. Thus, we must appeal to more than physics when describing a world that contains conscious creatures.

Here's a more formal presentation of the argument (taken from the SEP):

Premise P1Mary has complete physical knowledge about human color vision before her release.


Consequence C1Mary knows all the physical facts about human color vision before her release.
Premise P2There is some (kind of) knowledge concerning facts about human color vision that Mary does not have before her release.

Therefore (from (P2)):

Consequence C2There are some facts about human color vision that Mary does not know before her release.

Therefore (from (C1) and (C2)):

Consequence C3There are non-physical facts about human color vision.

This is, at first glance, a very plausible argument. Jackson's own conclusion was a version of epiphenomenalism: at the time of the article's publication, he held that whatever non-physical knowledge Mary acquired must lack any kind of causal efficacy, thus maintaining the causal closure of the physical universe. That seems to me to be a pretty desperate move, though, and apparently Jackson eventually agreed--he's since recanted this position, and now holds that there must be something wrong with the Mary case. I'm not sure if he's put any work into figuring out what it is, but other people certainly have. I'm going to more or less ignore all of them, as is my wont.

Here's what struck me when I was reading this argument today while preparing to lecture to the class on it: Jackson is deeply ambiguous, confused, or otherwise mistaken about what he means in (P1). The argument never even gets off the ground just because he's wrong about the kinds of things that Mary would be able to know from her particular position in her gray scale world. Let's tease this apart a little more.

What does it mean to say that Mary knows all physical facts about color perception? Presumably, just this: for every predicate, relation, or process P that relates to human color vision, if P is constrained by the laws of physics, then Mary knows P. This should be relatively non-controversial--"physical facts" are those (and only those) facts that are about the behavior of physical systems (and nothing else). The physicalist position is that the set of these facts is identical with the set of all facts that are necessary to explain the workings of the universe; that is, the physicalist position is the position that knowing all the physical facts amounts to knowing everything worth knowing. More narrowly, the physicalist position vis-a-vis color perception is just that knowing all the physical facts about color perception is both necessary and sufficient to give a complete account of how color perception works.

Good. We're homing in on the problem. The next question that we need to answer is this one: how do we go about learning physical facts? The physicalist "bite the bullet" style response to Jackson's argument just denies that Mary learns anything new when she's exposed to color for the first time--it asserts that if she knew all the physical facts, then she'd know what the experience was like. This is not very intuitive; we have a deep intuition that no matter how much I study some subject (via books, laboratory experiments, and so on), there are just some facts--like what it's like to see color--that just won't be accessible to me. That is, we have an intuition that there are some relevant facts that either can't be written down, or can't be discerned through objective experimentation: the what-it-is-likeness of color experience is, presumably, counted among these facts. This is the intuition that Jackson's argument exploits.

It's worth proceeding carefully here, though. Is saying that some particular fact F can't be written down or accessed through objective, third-person experimentation--that is, can't be described from a "view from nowhere"--equivalent to saying that F isn't a physical fact? Can all physical facts (to put it another way) be written down and accessed from a third-person viewpoint? Recall our definition of 'physical fact' above:

"Physical facts" are those (and only those) facts that are about the behavior of physical systems (and nothing else)
Let's rephrase the question, then: can all the behavior of every physical system be represented in third-person accessible formats? If we answer this question in the affirmative, we've adopted the position that Flannagan, in Consciousness Reconsidered, terms "linguistic physicalism," and there seems to be good reason to think that we've made a mistake somewhere in our reasoning. If we answer the question in the affirmative (that is), we've committed ourselves to the following position.

(LP) What it means for some fact F to be a physical fact is for F to be representable in some observer-neutral, third-person accessible form (e.g. public language).

That's a problem, though. If we adopt (LP), then Jackson's argument collapses into something that's trivially true (if not question-begging!).

(1a) Mary knows all linguistic (i.e. third-person accessible) facts about color perception.
(2a) Mary learns something new about color perception when she sees the rose.
(3a) Therefore, there are some facts about color perception that are not representable linguistically.

Of course this is true: it's part of what it means for something to be qualitative (that is, to be a conscious experience) that it's essentially private--that it's essentially accessible only from the first-person perspective. The question, then, becomes whether or not we are justified in adopting (LP); can we give an account of what's going on that doesn't require us to adopt it? Sure: we just have to allow that there might be some physical facts--facts about the behavior of some physical systems--that aren't capturable in third-person accessible representations. If we make this concession, then explaining what's going on in the Mary case becomes very easy: while black-and-white Mary has learned all the linguistically representable physical facts about color perception, this set of facts is not identical to the set of all physical facts about color perception--that is, there are aspects of the behavior of some relevant physical systems that cannot be captured from the third-person "view from nowhere." These facts, of course, are facts about what it is like to be in a certain physical state. To put it another way, there are facts about the state of Mary's own brain--which is, of course, a physical system--that can't be known from a third person perspective: she actually has to be in that state in order to know everything about it. When she's exposed to red for the first time, then, she's adding another bit of physical knowledge--which just is, recall, knowledge about the behavior of physical systems, which includes her brain--to her knowledge-base: that bit of knowledge, though, is one that is only accessible from the first-person standpoint.

Let me try to put this point as simply as I can. The problem with this thought-experiment is that Jackson is mistaken when he says that black-and-white Mary knows all the physical facts. What he means to say is that she knows all the linguistic physical facts--all the physical facts that can be accessed from the "view from nowhere." What Mary doesn't know is the set of physical facts--facts about the physical system that is her brain--that can only be accessed from the first-person viewpoint; she doesn't know what it's like to be in a particular physical state. That's what she learns when she leaves her black-and-white operating room.

To put it one more way, let me just say this. "Physical facts" is a term that refers not to a set of facts that is defined by a mode of access--that have in common something about how they can be known--but to a set of facts that is defined by the sort of system they deal with--that have in common a subject matter, not a kind of access. Physical facts are facts about the behavior of systems for which that behavior is totally describable in terms of the laws of physics, and it makes absolutely no difference (at least as far as we're concerned here) what the mode of access to those facts is. Some (many!) of the facts are expressable in observer-neutral language. Some are not. What matters is not this mode of access, but rather whether or not what is accessed is information about the behavior of a physical system.

Addendum: Please read the comment thread for more on this. Both Mark and Eripsa have given very insightful criticism and show that this argument needs refining. I've done my best to refine it below, and I might post an updated version later on. For now, though, the discussion in the comments is definitely worth following. Thanks to Lally, too, for providing vehement (and helpful) critiques off-thread.

Monday, January 12, 2009

Musings on Embedded Epistemology

I took a course in epistemology last semester, and (surprise) it made me think about epistemology.  What follows is an attempt to summarize my random musings and conversations I've had over the last few weeks into something that begins to approach a coherent theory.  It is, as I cannot emphasize enough, very prelimary so far, and very much a work in progress.  Still, I find these considerations very interesting, and I hope you do as well.

Belief justification is like a progress bar on a download--it can be filled or emptied to various degrees by things that we encounter out in the world. For instance, if I trust some individual a great deal, his words will tend to fill my "truth bar" a great deal; this weighing is based (among other things) on my past interactions with him, my knowledge of his epistemic state, &c.--certain; contextual variables about our relationship lead me to weigh his words highly when making (or contemplating making) epistemic actions like belief revision. The degree to which my truth bar is filled is also going to depend on the nature of the proposition this hypothetical interlocutor is informing me about: even from a trusted friend, I'm going to more readily assent to the proposition 'there is a brown dog around the corner' than I am to the proposition 'there is a child-eating clown around the corner.' Again, this reflects the contextually-influenced nature of epistemic action: based on other beliefs I have about how the world works, I'm going to be more or less likely to assent to a new belief (or to change an old one). 

It's important to emphasize that the truth-bar is almost never entirely full, except in some very special cases (e.g. conscious states to which you have immediate, incorrigible access). Take the case of a proposition based on basic sensory information--e.g. 'there is an apple on my desk.' In normal circumstances--good lighting, I can feel and see the apple, other people see the apple too, &c.--I; have very good reason to suspect that there really is an apply on my desk; the truth-bar for that proposition is (say) 99% full. Still, there are potential defeaters here: it might be the case that I am actually in some kind of Matrix scenario, and therefore it might be the case that there is no desk or apple at all. Still, based on other (fairly strongly justified) beliefs I have about the world, this Matrix scenario seems rather unlikely--that is, the truth-bar for 'I am in the Matrix' is very, very close to empty (though not entirely empty, as the proposition is still a logical possibility). Because this defeating proposition ('I am in the Matrix') has a very weak truth-bar, it doesn't weigh very heavily in my epistemic considerations--it's enough to keep the bar for 'there is an apple on my desk' from being 100% full, but that's about it. 

This goes sharply against established epistemic tradition, according to which the primary goal of epistemology is truth. If we define truth as a 100% full bar, there are going to be very few propositions (aside from tautologies like 'all black things are black') that will enjoy an entirely full bar. Instead, the right way to think about epistemology--and about our epistemic responsibilities--is as a quest for justified belief, a quest for a reasonably full bar. What counts as 'reasonably full' is, again, going to vary based on contextual variables: when the stakes are rather low, I might assent to a proposition when (say) the truth bar is over 50% full. This might be the case when, for example, a friend tells me that there is a brown dog outside my house; I believe him, and if someone asks me 'is there a brown dog outside your house?,' I will be inclined to answer in the affirmative. My friend might be wrong or lying, but the stakes are low and I have very few strong defeater propositions in play--few good reasons to suppose that my friend speaks falsely, in other words. In more important cases (such as when engaged in technical philosophical deliberation, or when designing a passenger jet), I'm going to be inclined to withhold assent from propositions until the bar is almost entirely full: the consequences for assenting to the wrong belief are so potentially dire, that I will demand a higher standard of justification, investigation possible defeaters more thoroughly, &c.; 

The emphasis here is on the contextually-dependent nature of epistemic action; rather than doing a lot of complex deliberating for every possible belief change entirely in our heads, we "offload" a certain amount of the work into the existing epistemic environment; that is, we use the existing epistemic landscape to simplify our decision-making by heuristically assigning various "values" to propositions that are related to the one under consideration, and performing a kind of Bayesian calculation to get a rough approximation of truth or falsity. We can make a direct parallel here with other work being done in extended/embedded cognition and extended mind theses--in just the same way that we use external props (e.g. written notes) as props to support certain cognitive processes (e.g. memory), we use our intuitive grasp of the existing epistemic landscape as a prop to support our own decision making. I call this approach "contextually embedded epistemology." 

Statisticians or those with a background in math will recognize that I'm describing something very much like a Bayesian network here--I suspect that our beliefs, were they to be mapped, would look much like this. There are multiple links between multiple different beliefs, and one belief might depend on many others for support (or might be partially defeated by many others). The picture is constantly in a state of flux as shifts in one node (i.e. a single belief) influence the certainty (i.e. the fullness of the truth bar) of many other nodes.  The Bayesian way of looking at things is far from new, but the emphasis on partial-completeness and environmental support, as far as I know, is.  These are just some random thoughts I've had about this in the last few days, so comments and criticisms are encouraged.  This needs a lot of tightening up.