First though let me reiterate the fact that there is a genuine scientific problem of consciousness (aka experience). Unfortunately attempts to ’save’ spiritual beliefs about souls by pushing this notion into the gap left between experience and physics has encouraged most hard headed scientist types to dismiss all talk of experiences as unfounded mystical crap. However, there is nothing contradictory about believing that experiences are real (I’m directly observing this right now), governed by a scientific law just like charge or mass but not (ontologically³) reducible to mere facts about position (or wavefunction) of particles and the like. In other words it’s true that what goes on in the brain completely determines what we experience but we have to go out and do science to figure out how. I can figure out that 2+2=4 without doing experiments but figuring out what configurations of particles feel pain requires I go out and see how things work in the real world⁴.

Hopefully continued neuroscience research will eventually yield a theory telling us that if a system of particles has n units of property A and m units of property B then it will be experiencing a mixture of 25% pain and 75% boredom⁵. Even though we don’t yet know what form this theory will take the fact we are trying to explain a fundamental natural property of the universe gives us some idea of what form we should expect the theory to take (Occam’s razor applies). For instance even though back in the 16th century Gallileo couldn’t possibly dream of the form quantum mechanics would eventually take he would have been justified in assuming that the ultimate physical laws wouldn’t mention St. Bernards, i.e., it would be very odd if the TOE was of the form particles behave like X unless they are part of a St. Bernard in which case they do Y.

Therefore since feeling like something is a fundamental natural property⁶ we can assume that there will be some simple property of a system which determines whether it gives rise to an experience or not. So far no problem, we just need to find some simple property that all the things we take to have experiences (people, dogs, etc..) satisfy when having experiences but things we assume aren’t experiencing (tables, anesthetized people) don’t. The difficulty is that such a property must allow a sensical evolutionary explanation of why we are conscious and experience the world in a unified, understandable fashion.

After all it could have been (if natural law was different) that our experiential lives weren’t hooked up to our behavior/environment in any coherent fashion. The efficient design of a visual system might have been such that seeing a particular sort of diagonal line created the experience of being in a small igloo while a slightly different line made one experience being burned alive. Moreover it could have been that rather than what seems a unified conscious experience each person would give rise to a myriad unintegrated experiences some occurring at a very low level (an experience arising from the module that does first pass filtering on our vision) and others at a very high level. Short of assuming miraculous good luck (evolution just happened to hit on the design that gave us unified, coherent experiences) this means that whatever simple physical property predicts the existence of experience must be (mostly) coextensive with efficient implementation of animal executive functions (so for example it doesn’t occur in my car radio).

This leaves two options for a plausible theory of experience. Either there is some simple computational property that characterizes the processing done in (higher?) animals and any device implementing that computation has experiences or there is some simple kind of (uncommon) physical interaction that is particularly well suited to implementing animal executive function (so evolution will likely select for it in just this case). I call the first theory the “magic algorithm” theory of consciousness. Presumably there is some magical couple of pages of lisp code so that only those objects implementing this code have experiences. I find this sort of theory pretty absurd on it’s face (not to mention the empirical evidence a century of AI failure gives us) but maybe it could be swallowed if this was the only problem. The bigger problem with the magic algorithm theory is that it asks us to accept that there is a well defined notion of implementing a particular computation. Also it seems apparent that any plausible characterization will require realism about causation, i.e, in order to distinguish genuine implementation of an algorithm from happenstantial agreement we must distinguish real causation from mere accidental constant conjunction. So not only does it seem doubtful that there is a well defined notion of implementing a computation but even if there was such a definition it would require metaphysical extravagance to work and is thus disfavored.

In summary this leaves us with the conclusion that there is probably some special sort of physical interaction/state (simply defined in terms of fundamental physical laws) particularly well suited to animal executive function and it is the existence of this physical interaction which gives rise to experience. Therefore merely simulating this process on a general purpose processing unit would not produce experiences. Note I’m not arguing that there is new fundamental physics in the brain like Penrose and others would have us believe. Certainly that is one thing that would fit my criteria but there is no reason that the physical correlate of consciousness couldn’t simply defined in terms of already identified types of basic physical interaction.

Then again on some days this argument just convinces me that induction is a load of crap and the only reason our physical theories have been so successful is that we are very well evolved to predict physical facts about our environment. If we give up on the idea that experience must obey simple natural laws then everything is up in the air (literally everything about the world, as we would no longer have a good reason to believe rotting tomatoes weren’t the most likely physical substrate of our experienced lives).

There are two possible views one might have about content (mental, linguistic or whatever). One view holds that there are certain events/relations/objects that intrinsically have certain content. That is what makes certain objects/states express content is a brute ontological fact. Searle’s belief that certain sorts of experiences just come with satisfaction conditions is a good example of this view. At the most basic level some components of the experience posses content like properties directly not as a consequence of any other facts about them. Alternatively you might not add content to your fundamental ontology and instead try and layer it on afterwards. For instance any attempt to define content in terms of counterfactual dispositions or other non-content bearing property. Let us call the former view content non-reductionism (CNR) and the later view content reductionism (CR). Note that the CR/CNR distinction is almost exactly analogous to the debate about ontological reducibility/irreducibility for experiences.

Generally any physicalist will hold CR as they obviously will be reluctant to add content to their fundamental ontology. While not logically required anyone who believes in content externalsim (e.g, supporters of the causal theory of reference) or is otherwise a proponent of broad mental content will endorse CR. Though some philosopher might endorse a crazy view like the extended mind hypothesis and thus reasonably hold both CNR and externalism it is a very rare and extreme view. The original and primary aim of most externalist theories is exactly to explain what gives rise to content they tend to be an alternative to views which hold that content is a fundamental constituent of reality.

In short most popular modern theories of content (Searle excepted) and almost all proponents of externalist theories of meaning endorse CR. This is particularly ironic as CR is incompatible with there being any fact of the matter about content externalism or a substantive dispute between internalism and externalism. Ultimately CR forces one to view content as a mere convenient approximation, much like classical physics and the supposed content it talks about is, like the rigid body, merely a useful idealization.

By definition content is not a part of the fundamental ontology under CR. Thus any statements about content are either fictional/formal (like mathematical statements about ideal objects) or reduce to a claim about objects in the fundamental ontology. Assuming that content claims aren’t totally formal then any physicalist must believe that claims about content are really heavily disguised claims about physical events. For instance the Kripke causal theory of reference must be interpreted as a (very high level) statement about the behavior of point particles (or strings or whatever). Already this should give one reason to doubt the more categorical claims about content as almost always high level approximate theories have exceptions.

In such a situation what it is for some theory of content, like Kripke’s causal theory of reference, to be ‘correct’ is simply to make accurate predictions. Since none of these theories aspire to give exact predictions about fundamental particle we can only evaluate it’s virtue as a convenient approximation as we do with classical mechanics. For the physicalist content externalism is only as good as the physical predictions it makes. In other words Kripke’s theory of reference is (approximately) ‘true’ if it gives accurate predictions of when people say, “Ohh yah he was referring to the such and such Socrates,” plus similar reactions.

Understood in this fashion we have no good evidence for content externalism. I tend to think our best predictive theory is the semi-internalist fold theory. But regardless of where you think the evidence lies the best theory of content would be an empirical matter to be studied by psychologists/anthropologists/social scientists. It doesn’t even make sense to employ the sorts of thought experiments about twin earth commonly used to argue for content externalism since the possibility that content externalism is literally true isn’t even on the table. Besides these thought experiments would now come out against content externalism. For instance it’s absurd to make the predictive claim that people wouldn’t (eventually) respond to swamp man as if he really was referring (even with words he has never heard).

Now I expect a few objections at this point. One might claim that content externalism is an idealization and these thought experiments shows the internal coherency of the idealization. However, once we know a theory (like classical mechanics) to be literally false purely theoretical virtue takes a back seat to pragmatic value and the theory fails in it’s original intent either way. Also one might try and claim that content externalism was merely a definition of reference, i.e., saying it is a fully formal theory. Yet if so this whole area of philosophy is not only misdirected but actually misleading. Content externalism would then be a pretty uninteresting branch of mathematics with fancy names that tricked us into thinking it was saying something about pre-theoretical notions of content or meaning.

The argument goes through just as effectively only assuming CR rather than full on physicalism. It doesn’t matter whether we have to reduce claims about content to fully physical properties or to some other (non-intrinsically contentful) set of properties. In either case it just doesn’t make any sense to talk about theories like content externalism being ‘true’ in any sense other than an approximate or trivial one. They certainly aren’t saying what they intuitively claim (there are actual states that have content prior to the theory and the theory describes how that content works).

The upshot of all this is that there are pretty much three choices we can take as philosophers when dealing with content.

1) Give up Kripke and Davidson and (like Searle) accept that content is really a basic constituent of reality.

2) Give up the idea of content as anything but a folk concept and leave it to the scientists to generate/test theories about how we actually assesses content.

3) Accept that we can only give approximate predictive type theories and try to come up with a simple theory describing actual human/societal norms about assigning content. Effectively we would be doing much the same thing that people do when they compile the rules of grammar. There is nothing ‘true’ or deep about the rules of grammar but a precise agreed upon statement can be helpful as might also a catalog of the societal norms about ascribing content. This too might require experiments.

In any case take the (far too) widely assumed thesis of strong AI, namely that any two processes that execute the same calculations will have the same experiences. For instance any computer that simulated the human brain would have all the same experiences as that person. Note that this is much stronger than merely saying we could build some machine that simulated the human brain and had the same experiences as it tells us that it doesn’t matter how we simulate it.

Now in order for this thesis to make sense we must have some notion of when a certain physical device implements a given calculation. Of course the natural way to phrase this is in terms of some kind of counterfactuals. However, this means that we would need to buy into a substantive notion of physical cause. There would need to be an extra meta-physical entity that somehow makes one description of the actual events in the universe the ‘true’ laws that really support counterfactuals while other predictively equivalent ones are wrong. Note that being a Lewis style realist about possible worlds is not sufficient either as you would need to believe that the closeness relation was somehow real/had metaphysical backup as well.

In fact if we are Humans about causation it seems that there is no hope for us. Since there is no (objectively) privileged statement of the laws we can transform any actual result into a computation. If we want to conclude that the decay of an atom implements a certain calculation we just decide what the output of the computation should be (say 1) and pick an equivalent (in our world) formulation of the physical laws that says (assuming the atom did decay) the atom decays if and only if the output of the computation is a 1. Obviously if we want to break up some complex computation into many small pieces we surely can. In particular we can interpret the random thermal motion of a table to be the simulation of a brain.

Now perhaps you will try to object that simple descriptions of the laws are somehow privileged. Even if so it seems you still need some fact which makes them objectively privileged. If all being simple amounts to is that human beings take a certain attitude toward them you haven’t gotten very far. It would appear that the very intuitions that motivate the strong AI view, namely that there isn’t extra spooky non-physical facts that determine what events cause experiences, is undermined as the very position sees to require we have these non-physical facts about what the ‘right’ way to write the physical laws is.

Probably this argument has been made in some form before but it occurred to me today and I’m stalling on my math.

Can positivists make sense of the notion of Nietzsche’s repeating universe or would the notion be rejected as nonsense? Of course they couldn’t make sense of the actual stuff out in the world (independent of perception) going through the same motions but can they even make sense of the repetition of experience, i.e., that my experiences will repeat infinitely often.

Just as interesting is whether the positivist can distinguish the situation where the universe happens in the standard fashion with experiences occurring in a particular order and the situation where those experiences are mixed up in an arbitrary fashion or don’t have any temporal order at all. Of course since each complete experience would include the feel of memory and temporality it doesn’t seem there is any difference between these two situations in terms of sense data.

Or to give one simple example of this question does it make any sense to say that my experiences of the world around me don’t occur until five minutes after my interaction with the environment, i.e., there is a lag between what happens to my body and the actual qualitative experience. How would one even make sense of this question on a non-positivistic account?

Also does a positivistic account require some primitive notion of an experiencer in addition to the experience itself. That is can a positivistic account distinguish between situation A where Bob and Fred go through their lives as normal having their regular experiences and situation B where Bob and Fred have their normal experiences up until time t after which Bob has what would have been Fred’s experiences and vice versa. Since both situations involve exactly the same experiences existing (at the same time even…modulo relativistic issues with simultaneity) it is tempting to say no.

However, if we take what I think to be the right answers to these questions (no positivism can’t make a distinction) we end up with a system where all statements must reduce to pure quantifications over experience, i.e., every statement is something like a first order quantification over all the experiences that ever have and ever will exist but without any access to that temporal data. This approach is very appealing but it poses major problems for philosophy of science. In particular we might be able to justify positive statements via induction (if there is an experience of being person X and taking LSD there is also an experience of being person X, having taken LSD and being really fucking high) but how could we ever justify negative statements. Presumably a statement like, “Milk is not a psychedelic drug,” would mean something like, “Generally if there is an experience of drinking milk and being person X there is not an experience of having just drunk milk, being person X and being really high.” Of course I would need to fill in a bit more to those statements to make them truly correct but I think this illustrates the idea. Supporting negative claims would require something like inductive evidence that certain sorts of experience don’t exist and, absent some kind of a priori assumption about experience being instantiated by physical systems that a positivist shouldn’t make, there seems no way we could collect such evidence.

Ultimately this is motivated by my intuition that there is something deeply right about positivism. Our understanding of the external world must ultimately be based on our experiences because those are the only things to which we have access. Where the positivists went wrong is in assuming the world presented itself to us in this very narrow form of experience termed sense data that resembled the way a camera or microphone might record the world when in fact much unconscious processing goes on which allows the world to be directly presented in terms of complex concepts (affordances, shape, social relation etc..). However, I am still trying to work out exactly how to make this intuition precise.

I remember hearing about neo-positivists many places but I also seem to remember having them explained to me once and dismissing them as silly or just doing something I didn’t find important/interesting. But if there is anyone who does this sort of stuff I would be very interested.

So from several quarters lately the question of what it means for a perception to have content. Not only did the issue come up in the Working group in the philosophy of mind, and in Searle’s seminar on Language and Consciousness but separately a girl I’m seeing asked me the same question. I figured this meant I really should write a blog post on the subject but every time I thought I had a handle on the subject I would learn yet another subtlety of the issue. I’m still far from an expert, and this post could turn out to just be deeply misguided, but I wanted to get my thoughts out here and see what people think. The arguments that have motivated my thoughts on these matters are mainly the things we have been reading in Searle’s seminar this term: Dretske’s “The Intentionality of Perception” found as chapter 7 in the book John Searle edited by Barry Smith, Searle’s book Intentionality, McDowell’s piece “Intentionality De Re” in Searle and His Critics as well as Searle’s reply in that same book. Plus of course general background from Chomsky and one other article of his (I am in the process or reading) which I will cite later. Though motivated by these pieces I assure everyone my thoughts are entirely my own and no one else should be held responsible for any mistakes (or brilliant new observations) I make.

The first difficulty in deciphering what it might mean for a perception (say the visual experience of looking at an olympic figure skater) to have content is defining what we mean by content. Unfortunately doing this in any generality is beyond the scope of this post and quite possibly a hopeless endeavor, i.e., there are several different things we mean by content. So we can get on to the real meat of this issue let me gesture in the direction of what it means to have content by saying that a perception that has content represents the world as being a certain way. So one way of having content might be to have an attached proposition, or to have something like Searle’s conditions of satisfaction. Whatever the mechanism for a perception to have content it must be possible for that perception to be mistaken not merely misleading. So an uninterpreted picture can not have content, it may be taken from a strange angle which encourages people to draw incorrect conclusions or even be a picture of something physically impossible but absent interpretation it is just colors on paper and doesn’t represent the world to be any particular way (this is not to assume that a picture plus certain customs/practices/context/observation might not have content).

So at this point it might seem fairly obvious what it means to say a perception has content. A perception has content if it represents the world to be a certain way and as a purely linguistic analysis this may be correct. However, arguments like the one between Dretske and Searle over whether perception has content are meant to be substantive not merely linguistic differences over where to draw the line between perception and belief. At first glance, however, it seems difficult to see how any reasonable philosophical view could not be made compatible with either option (perception has/doesn’t have content) by slightly shifting this line between perception and belief.

No philosophical view is going to deny that my perception of the olympic figure skater almost immediately produces beliefs (that girl is really flexible, that trick is amazing). Nor is any reasonable philosophical view going to deny that if I had seen this same image in a different state and hadn’t generated those beliefs there would still be something in common between my two visual experiences. Yet now if I define perception to include those beliefs which are quickly generated (maybe not those examples) it would seem that perception has content but if I define perception to be those properties (in the metaphysical sense of things in virtue of which entities are similar) of my experience in common between viewings of the same light input to my retina it would seem that perception does not have content. So if we wish to retain the idea that arguments over whether perception has content are substantive we are going to have to do a bit better.

Having thought about the issue for awhile, and considered what the various philosophers mentioned at the beginning have said, I’ve come up with several possible interpretations for the substantive content behind the statement “perceptions have content.” Importantly when I talk about different viewings of the same image with different content I mean a hypothetical comparison between two situations where the same photons hit your eye but you end up representing the world in different fashions. In other words something like the face/vase figure-ground example but with actual differing content, i.e., you actually represent the world as showing you a vase in one case and a face in the other.

1. There is some meaningful (nonlinguistic) notion of what it means to be the same experience and “perceptions have content” asserts that there are no distinct experiences which don’t have content. Or in other words there is no one sort of experience we could point to that (like sense data) stays the same between viewings of the same image with different content.
2. The visual ‘image’ we have in our mind is genuinely different depending on the content we assign the perception and there is nothing else we can separate out we could call the ‘image’ that does remain the same. In other words if we were asked to describe the colors, curves, etc.. that we see our answer would be different depending on what content we ascribe to our perception of the image. Interestingly there is some scientific evidence for this sort of thing.
3. Seeing the same image with different content is very qualitatively different
4. The things which two viewings of the same image with differing content have in common are not a natural kind.
5. While their may be experiential components (or sub-experiences or something) which are in common between viewings of the same image with different content the content of our visual perception does not ‘rest on top’ of these components, i.e., the content and the ‘mental image’ are presented to our consciousness ‘at the same level.’
6. It is somehow impossible (physically? logically?) to have any visual experience with some associated content (this might be trivial content like “this is an image”)

I’m sure there are some possible interpretations I’m missing and I would love to hear other ideas people have. I suspect Searle means something like 1, 2 or 3 (though would probably agree with all except the last two) but I’m not entirely sure. At the very least I hope this post convinces people that the notion of perception having content needs more elucidation.

One interesting consequence of the idea that the statement “perception has content” should not merely be a statement about how we use language is that the content in question cannot be provided by some kind of simplistic content externalism. Active content externalism as Clark and Chalmers discuss in The Extended Mind which suggests that the supervenience basis of experience actually extends outside the brain and thus different objects which produce the exact same neuronal response in your brain may still cause different sorts of experience could still make this statement have substantial content. However, if by content we merely mean some linguistic tradition which tells us how to map certain personal/intentional states out onto the world almost by definition this is going to make the truth of the statement merely depend on how we use language. Of course you may not find this sort of ‘failure to be substantive’ problematic but it deserves point out that the notion of substantive I am using here rules it out from the get go.

I can’t help shake the feeling that this post may be kinda hard to understand. Maybe I will take any feedback I get and try to put things in a bit more coherent fashion in a couple days. At the very least I hope to come back and discuss some pluses and minuses for the various interpratations soon.

One question I have been puzzling over for awhile is whether allowing random phenomena in scientific theories allows us to create a theory explaining any collection of observations. That is if the world is actually too complicated to be described by a theory comprehensible to us can we make up a theory which appears to describe it by postulating randomness in the basic behavior of the universe? The answer, which was a lot simpler than I had been making it, is yes. No matter how complicated the universe turns out to be we can always come up with some theory which makes it look understandable but with some random elements.

This has some serious implications for realism and philosophy of science. In challenges the idea that the success of probabilistic theories like QM is evidence for their truth. It also illustrates the need for philosophy of science to address the question of what conditions can justify the retreat to a probabilistic theory. Unless we are to abandon the realist agenda or stipulate faith in the computable nature of the laws of nature we can’t accept a probabilistic explanation just because no deterministic explanation suffices. Thus putting the realist credentials of Quantum Mechanics in even more trouble.

I think this argument is interesting enough that it should be out in the literature so I’m particularly eager for comments. If anyone has any suggestions about how it could be fleshed out or how/if I should try to make this into a paper let me know. Any references to related literature would also be quite helpful (Kelly too since I haven’t read all his stuff).

Really Short Summary for Logic Student

The short version of the argument is as follows. If this goes over your head read the rest of the post.

We can idealize scientific observations as a real (infinite binary sequence). You can either think of this real as giving the list of all future observations or as coding a function between initial conditions and experimental results. The problem of finding a scientific theory thus becomes finding some algorithm which computes (predicts) the real since it is reasonable to assume testable scientific theories must make predictions computably. However, since there is a Martin-Lof random computing every degree if the universe we wish to describe is not computable we can always find some apparently random sequence relative to which it looks like we have a successfully sscientific theory. Since all we ultimately observe are the results of experiments this situation appears to be one in which some theoretical entity exhibits random behavior (given by the random real) which ultimately have observational consequences (with a mechanism given by the Turing reduction).

The Long Version

In order to apply the machinery of computability theory to the problems of scientific inference we first need to make some idealizations. Admittedly some of these idealizations are a bit crude. This is one of the areas I think needs work. However, I think they are accurate enough to allow us to draw real conclusions from them. If you are unfamiliar with computability theory this entry in the Stanford Encyclopedia of Philosophy gives a fairly complete introduction.

We idealize observations about the world as an infinite (length w) binary string (a real) or equivalently as an infinite string of integers. Call this real O. I think the best way to think of this idealization is as a mapping between the initial conditions of every experiment that will ever be conducted (actual physical experiment) and the result of that experiment. Alternatively we could use a real coding the sequence of all human sense data (i.e. experiences not some Carnapian sense data language) or we could restrict either representation to a particular class of observations, say those which count as physics experiments. The important point is that we can idealize all the observations that can every be made about the universe as a countable set on integers. Since it is reasonable to believe we could capture more and more subtle details of scientific practice by choosing better ways to code things into this real it is reasonable to think conclusions from this idealizations apply to actual science.

We take the test of a scientific theory is the ability to predict results of experiments from initial conditions. Modulo finite amounts of information which can just be embedded into the theory this ultimately amounts to computing the real O we mentioned above. Thus we can take a correct scientific theory to be a function giving us the values of O. Clearly though our scientific theories can’t just be arbitrary functions. It must actually be possible for us to use this function to predict results. Unless you believe Penrose and think humans can intuit things in principle beyond the capability of Turing machines this means the scientific theory must be computable.

If the universe is nice and has computable dynamics (i.e. the future states of the universe are computable from initial conditions) everything is good and we have no problem. O is actually computable and some computable scientific theory calculates it, i.e., makes the right predictions about the universe. What happens if the universe follows non-computable pattern? Certainly in this case we couldn’t come up with a scientific theory which can completely predict every observation, i.e. every bit of O. However, in modern quantum mechanics we don’t predict the outcome of every experiment with certainty. Instead we predict them probabilistically theorizing some inherently random events to explain the results of our observations.

So at the moment we have this picture where given any scientific experiment with particular initial conditions we can look up the experiment in our real O and retrieve the results of that experiment, i.e., O represents how every experiment scientists perform turns out. Thus a successful scientific theory is a computable function calculating O. If we want to allow a theory to postulate some kind of randomness as QM does we need to allow a scientific theory to predict results only relative to the outcome of these random events. The picture now is that given any experiment our scientific theory does not attempt to predict a definite result but instead identifies some collection of random events and tells us how the experiment will turn out for every way the random events could turn out. Doing the same thing we did with our experimental observations we can code the results of all the random events into a new real R. Even though an actual theory is likely to have random events with many different probabilities and possible outcomes these can all be coded into sequences of fair binary random variables¹. Thus we can pretend all random events are coin flips and code them into the infinite binary sequence R.

Now for a probabilistic scientific theory to appear to describe reality we only need a computable function calculating O from R, the outcomes of the supposed random events. Given this understanding when will it appear as though we have a valid scientific ttheory? Whenever there is some computable function calculating O from R where R looks random. So long as R looks random and we compute O correctly the situation appears exactly as if we had a valid scientific theory describing a universe with some inherently random events.

There is a great deal of literature about what it means for a real to look random but certainly a Martin-Lof random should count. A paper introducing the various definitions can be found here but the key point is that a Martin-Lof random real is completely unpredictable by any computable means. Importantly a Martin-Lof random is not even statistically predictable in a computable fashion, i.e., to any computable process a Martin-Lof real is indistinguishable from a series of truly random coin flips. Or more precisely no computable function betting on the bits of a Martin-Lof random can make arbitrarily large amounts of money. Thus anytime we can find a Martin-Lof random real R and computable function calculating O from R we have an apparently perfect probabilistic scientific theory.

Now the key point is this. Every real turns out to be computable in some Martin-Lof random. In other words no matter what the true nature of natural laws they always appear to be either computable or computable consequences of random events. Induction in some sense is always guaranteed to succeed so longs as it gets to consider probabilistic theories. If we live in a non-computable world we can always stipulate theoretical random events and create a theory which explains our observations in terms of these random events. Of course in reality what happens is the opposite, we look at the observational results and infer the values of the random events from these and then check that the supposedly random events occur with the right frequencies and without apparent pattern. The above argument establishes that we can always find some computable theory whose random events have the right frequencies and show no detectable patterns.

Repercussions for Realism

The result seems very damaging for realism, especially when our best scientific theory is probabilistic. Of course one could always try and take the hardliner and claim that if we have to resort to random events in our ideal theory their really are actual random events in the actual world. Yet these seems untenable as their are plenty of non-computable ways for the universe to work which don’t intuitively involve any randomness. For instance the actual natural laws could have some short and simple definition in terms of 0”. Since 0” can be expressed in a very simple and totally definite manner we could even live in a world which worked on very simple but non-computable natural laws. However, our scientific search for natural laws wouldn’t discover these laws but instead tell us that there were in fact random events and predict the results of experiments only probabilistically. Intuitively it seems there are a great many ways the world could be which would cause induction to ‘get it wrong’ but appear as if it got it right.

I tend to think of languages as a kind of publicly available technology which people learn to use (rather than of everyone speaking their own language, to which they impart their own intended meaning, which everyone else has to figure out), so I’m less inclined than Frege to say that it is individual speakers’ intentions which make it the case that, say, the first person indexical is a singular term.

I just don’t understand what talk about language meaning over and above the intentions of the speakers is supposed to mean. This isn’t to pick on Gillian the practice is widespread in the philosophy world. I keep hearing these rumors from everyone that there are powerful arguments why we can’t just drop back on the reality of internal content and consider language as just a pragmatic device to communicate this content but I have yet to hear any of those arguments. Since I was never one to be impressed by authority here goes anyway. To be clear I’m not denying that there can be interpersonal ‘facts’ about meaning. It is just that these are facts the same way “That girl is hot.” is a fact. There truth is entirely dependent on certain shared attitudes for the audience. If what people found sexually attraction changed so would the truth of the statement. The same is the case with meaning, if what people intended by their use of a word so would its meaning.

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p> Some might rightly object is that all I have shown is that facts about meaning supervene on facts about intention. This is indeed the case but it still leaves the defender of meaning in a tight bind. He must either stipulate some special metaphysical reality behind linguistic facts or grant that they are reducible to facts about intent. As I tend to suspect the motivation for preferring interpersonal facts about language over personal fats about intent is Quineian I very much doubt the defenders of linguistic facts would be happy with such metaphysical overhead.

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p> Of course if you are willing to take a fully Quinean line you wouldn’t really be in an dilemma at all. If you think truths about intent can be exhausted by challenge response answers then this is all perfectly sensible. If on the other hand you believe in real facts about intent debating about interpersonal linguistic facts seems silly.

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p> In other words once you accept that interpersonal linguistic facts are reducible to statements about intent any debate about interpersonal language fact becomes just a disagreement about terminology. Any disagreement about interpersonal linguistic notions is either really a psychological question and thus not really of philosophical interest. For instance questions about whether water means ‘H2O’ or the natural kind which lives in rivers are really just questions about what most people intend when they use the word water. Alternatively the question is really just one of terminology. For instance by the meaning of a word do we intend to refer to what people intend the word to indicate now or their dispositions to change that reference in the face of new evidence.

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p> In either case I see little philosophical utility in questions about meaning that are not simply questions about individual meaning or intent. Now perhaps I am missing something and people really do believe there is some metaphysical reality which makes interpersonal linguistic statements true or false. However I have yet to see any satisfying explanation.

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p> Well I suppose I shouldn’t make bold statements like that without explanation so here goes. So first I am going to argue that it is not sentences which inherently have truth values, nor propositions. Rather it is mental representations. Essentially I agree with Searle when he defends the thesis that many experiential states like belief inherently have conditions of satisfaction. Certain of these experiential states we judge to be correct or incorrect (true/untrue) depending on whether their conditions of satisfaction are satisfied or not.

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p> Sentences then are said to be true if they induce the right kind of mental representation and the conditions of satisfaction of that representation are met. They are false if the conditions of satisfaction are not met and neither true nor false if they don’t evoke the right kind of mental state. Admittedly more needs to be said about what the right kind of mental state is here. It certainly isn’t belief as we can judge the truth or falsity of sentences independently of belief but this I will leave to later.

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p> Now the reason the liar and strengthened liar are problematic is that as well-formed sentences they seem like the sort of thing which ought to be true or false or correspond to a proposition. If we could give a compelling justification of why liar sentences should not get truth values or correspond to entities which get truth values this would address the difficulty. We could then insist that sentences like the liar as well as the strengthened liar aren’t true or false anymore than ‘asdfujknsdfkj’ is true or false. In other words despite their apparently acceptable surface structure they really aren’t making claims.

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p> Since I understand sentences to be true or false depending on the conditions of satisfaction of mental representations the next move is pretty obvious. I deny that liar sentences correspond to the correct sort of mental representations. Essentially my claim is that these sort of mental representations can only have conditions of satisfaction which refer to external reality or which refer to the correctness of already formulated mental representations.

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p> So in other words I am arguing that these mental representations are inherently stratified in a similar way to what Quine requires for comprehension instances in New Foundations. Admittedly one might ask what extra work does the theory of mind stuff do, why not simply insist on this directly in our theory of truth. My response is that these restrictions seem ad hoc and unmotivated in a theory of propositional truth. However, I think an understanding of theory of mind can independently motivate this condition.

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p> In effect this lets us justify these restrictions on truth by reference to empirical observations. I certainly find that when I hear a liar sentence I don’t create a mental representation with conditions of satisfaction like I do when I hear a normal descriptive sentence. This no longer needs to be justified as some reasonable property that truth must possess but is now simply an empirical fact about our mental experiences. Sure one might wonder what things would be like if this wasn’t the case but then one just isn’t talking about the same notion of truth.

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p> Sure more work needs to be done to spell this all out satisfactorily but this is at least explains why I think the solution lies somewhere in the philosophy of mind.

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p> For more explanation and some compelling arguments in favor of mental events inherently having conditions of satisfaction read Searle’s Intentionality.