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Is the “external world” real?

Jason writes about the existence of God, and one of the questions that arose is how one justified induction. Jason writes:

First, on induction: I disagree that I accept the utility of induction by means of faith. This inference seems to rest on a false dilemma, namely that we accept all propositions either by induction or by faith.

Other means exist besides these two. In the case of induction, I simply find that rejecting it leads to a sort of mental paralysis, one in which I can permit myself no thoughts at all about the external world.[2] Worse, whenever I try to think this way, I always fail. Following Kant — I think — the inductive aspect of our reasoning may well be a priori. We’re stuck with it, whether we want it or not.

As such, we might as well make the best of it. I take this to mean putting my inductive inferences into the least contradictory order that I can. It’s that or I go back to paralysis.

This seems more like a pragmatic reason to act as if the world we experience is real than an apriori reason to believe. Apriori epistemic reasons are not the same as reasons we have to accept in order to avoid paralysis. After all, I could consistently say that it is not clear if the world we experience really exists but there are pragmatic reasons to treat it as such anyway. I will give such an argument later. Jason may as well concede that he has no argument to show that the probability that the word really is as or close to how we experience it is close to 1. And that is required in order to vindicate the common sense belief that the world we experience is real.

Veronica Dire writes:

Right. I consider “brain in a jar” or “Descartes demon” scenarios so far fetched to be irrelevant. They are curiosities to while away the time. Thing is, nowadays we know a fair amount about how brains work, how our senses work, how learning works — not everything of course; there is a long, torturous path between what we know and what we would like to know, and we may never travel the full distance. But we know a lot. Epistemology is today an empirical science. And “the thing in itself” is atoms and particles and complex forces, and we know that we can never perceive the full thing. Our abilities to measure are very limited. Our models are imperfect. Our theories go so far, but there must be further, some next layer of turtles we have not yet puzzled out. But to jump from this manifest ignorance to phenomenology, or worse, God, simply is not justified. Such is fanciful and nothing more.

She is just wrong about this. Evil demon or systematic deception scenarios are relevant and cannot be ruled out just because they sound strange. Consider how we would try vindicating such a move. If someone were to ask us why we think that it is unlikely that an evil demon is deceiving us, we would say that it is far fetched, i.e. it lies too far away from things which we have experienced. But this circularly assumes that we have till now not been deceived by evil demons. If an evil demon did in fact deceive us, we would not be aware of such deception. Thus, we cannot claim to have not encountered any evil demons without presupposing the conclusion that we are trying to justify.

Evidentiary Relation and Possible Worlds

The construction of these sceptical scenarios strikes at the heart of fundamental questions of epistemology. Consider the following principle/definition which everyone should accept.

Evidentiary Relation (ER): Some R counts as an epistemic reason for a proposition P if and only if R being true makes P more likely to be true and R and P are distinct.

Cases when R is identical to P, that is self evident propositions are justified differently.

Self Evidence: A proposition P is self evident if and only if its negation is logically impossible.

To illustrate how ER works, I will provide an example. For the purposes of the example, I will set aside the various sceptical scenarios

Suppose I experienced seeing five green books on a shelf. The fact that I experience seeing five green books on the shelf makes it more likely to be the case that there really are five green books on the shelf. It might turn out that I was miscounting the number of green books. Therefore, the fact that I experienced seeing five books is not dispositive. One way to spell this out is to use the possible-worlds framework. In some possible worlds, the shelf has only one green book. Of those possible worlds, the fraction in which I experience seeing five green books is very low or even zero. We can similarly describe probabilities of me experiencing five green books when there are other numbers of green books on the shelf. All counted in, we should expect that in most of the possible worlds where I experience seeing five green books, there are in fact five green books. This proportion goes up once we start excluding possible worlds where I am drunk, sleepy or cognitively impaired in other ways. In addition, there is, for lack of a better term, a “story” we can tell that accounts for how it can be that our experience of seeing five green books stands as evidence for there being five green books. In this case, it happens that there is some plausible causal story that we can tell. Quite plausibly, we can posit that any perceptual capacity must involve some causal mechanism by which information is transferred to the receiving perceptual structure. If there were no causal mechanism, it would seem impossible that the perceptual structure would be able to obtain information about the fact in question.

The only constraint on any account is that the account must entail that we have the experiences we think we have.  Even when we relax the constraint against sceptical scenarios, our own subjective experiences still constrain possible accounts. We cannot be deceived into experiencing something we are not experiencing.

Each account is logically connected to our experiences. The confidence we ought to have in any one account just is the fraction of accounts occupied by that account. There are a number of upshots.

1. More specific accounts are less probable. This is to be expected as we would need more evidence to fill in details.

2. Accounts with fewer premises that are not inferred from any other premise are, all else equal, more probable. This is because the probability of a given account is equal to the product of the probabilities of its independent premises.This gives us a nice derivation of Occam’s Razor.

3. Things like gravity, strong force, weak force and electromagnetism are thus (at the minimum) logical objects we posit in order to make the content of our subjective experience more probable. In fact, positing the existence of such logical objects which entail our subjective experiences makes for a good explanation as possible worlds in which we merely happen to have the experiences we have without any uniting explanation are improbable for reasons mentioned in (2)

4. Once you posit the existence of such logical objects, the expectation that future events will look like past ones is almost trivial. The existence of those objects entails that certain future experiences will occur. That we are only highly confident about the existence of such logical objects just means that we will only be highly confident about what our future experiences will be. This solves the old problem of induction

5. It is possible that the new problem of induction could be solved as well. Given that both grue and green have the same phenomenological character before time t, the story that connects the wavelength reflected from the emerald to the perception of green/grue should be the same. However, the details of any such story should make it unlikely that the phenomenology would change at time t. If there is a story that logically links physical property to phenomenology, then there is no reason to posit a change in phenomenology absent some intervening cause. Any story about a grue object would have to posit some such intervening cause in order to spell out what a grue object would be. This could, depending on the explanations available range from being only slightly more complicated than explanations involving green or involve so many more moving parts as to be very nearly precluded. This largely depends on what the most plausible story about grue is.

Sceptical Scenarios and Possible Worlds

Till now, I have mostly bracketed away the possibility of evil demons, brains in vats and other sceptical scenarios. However, we can consider that for just about every sort of possible world in which the various objects posited are real, we can imagine conceptions of justice in which they are systematic deceptions of one sort or another. Even if such scenarios are more complicated than the realist ones, they are not so complicated that the realist option becomes almost certain. As I wrote in Jason’s previous post:

Brain- in- vat is merely a place holder for a whole class of theories in which we are systematically deceived by some mechanism. By eliminating narrative details, we can posit two worlds. W1 describes a possible world (or a class of possible worlds) in which we are not systematically deceived in some serious way. W2 represents a possible world (or a class of worlds) in which we are systematically deceived*. Let us now consider how many more moving parts are necessary for W2. Logically, we do not need to posit anything else in this world other than the content of the deception, the mechanism of deception and the person being deceived. This is at most two or three more moving parts. W2 is thus negligibly more complex than W1. Let me grant that the mechanism of deception must have at least as many moving parts as the content of deception. If I grant this, W2 has just twice as many moving parts as W1. Since it is the case that we are either systematically deceived or we are not, we get two equations

p(W1) + p (W2) = 1 …………………… (1)
p(W2) = p(W1) x p(W1) …………….. (2)

solving for p, p(W1) = 0.62

So while we have more reason to think that we are not systematically deceived than to think that we are, the reasons are not so strong as to warrant the near certainty with which we attribute to the “external world is real” proposition.

So, even if not quite equal in number, it seems that there is still approximately a 0.4 probability that we are deceived. This means that we should be closer to reserving judgment i.e. being indifferent between realism and anti-realism than we are to endorsing realism.

Notice however, that even in the anti-realist scenarios, the deception has to have most of the same properties as the real world. The sorts of rules that relate particular features of the deception to the subjective experience will have to be the same. In fact, the key difference is just the metaphysical status of the objects of apprehension. Illusory food still tastes the same way and has the same effect on illusory body in mass deception world as real food has on real body in realist world. Since this is the case, we can just say that our normal inductive practices tell us things about the world that we observe without committing ourselves to whether this is real or illusory.

Consider a cup of cocoa. The reason why the hypothesis that there is a cup of cocoa in front of me is highly probable is that there are few other stories to tell in which I see the cup, and where when I further see my hands touching the cup I also feel the cup, and the heat of it. When I further pick up the cup and drink the cocoa, I only taste the cocoa when it lands on my tongue. It is not logically necessary that all these distinct sensations coincide. Positing the existence of a single object which has certain properties explains the coincidence of sensations. Consider what the evil demon would have to do to reproduce this. He would have to reproduce in every sense but one, all the properties of a real cup. Out of all the sceptical scenarios, the ones in which there is an illusory cup with illusory cocoa is the most likely scenario. That is, of the various theoretical explanations of the illusory properties, the same sorts of reasons that impel us to think that there is a real cup of cocoa would also incline us to think that there is an illusory cup of cocoa in the illusion case. So, we can know that there is a cup of cocoa. We just don’t know whether it is illusory or real.

To further complicate things, when the illusion is so complete, the difference between illusion cocoa and real cocoa seems merely semantic. After all, there is a sense in which the illusion exists too. After all, if the illusion did not exist, there would be no way in which the illusion could produce experiences in us. Real and illusory, then in these sorts of cases seem to be some obscure metaphysical properties which may not really matter for most purposes.

Practical Implications

In addition, suspending judgment about the metaphysical status of the world we observe does not change which courses of action are more rational to pursue.

Consider the following example where we decide whether to attempt to jump off a building

If the observed world is real, U(Jumping) < U(not jumping) given that we care about living and are reluctant to die.

If the observed world is not real, maybe nothing would happen to us if we did try to jump off a building. Perhaps something good will happen. Perhaps something bad will happen. Either way, based on the principle of insufficient reason, I have no expected change in utility even if I do jump. We can thus assign our utilities for jumping and not to be some value k

Given that we adjust our probabilities according to the calculation given above, the expected utility for jumping is

E(U-jump) = 0.4 x k + 0.6 x U(jumping)

E(U-no jump) = 0.4 x k + 0.6 x U(not jumping)

E(U-jump) < E(U- no jump)

In fact, since it seems that the expected utility is always going to be transformed in some monotonic way, the preference ordering is undisturbed and the ranking of various courses of action remains the same. Worries about pragmatic consequences of suspending judgment are in this case unwarranted. Whichever course of action is rational when we know that the external world** is real would be the same even if we suspended judgment about it.

We thus don’t have to assume that the external world is real in order to do science or go about our daily lives. At most, we just have to acknowledge some possibility that the world we observe is real as far as daily practical problems are concerned. On the theoretical end, we just have to be careful and be modest about the claims that we can make. However, as we have seen, this does not invalidate our current scientific knowledge.

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*it is irrelevant whether this deception is caused by some agent. All that is relevant is that the mismatch between reality and perception exists.

**There is a sense in which there has to be a world external to us. The question I am concerned with is whether the world that seems to be external to us is real.

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57 thoughts on “Is the “external world” real?

  1. I think I basically agree. We don’t really know what the world is really “like.” In a sense it’s impossible because anything that the world is “like” is a perception, not a property of the world. the world is a radically different thing from any perceptions of it, and questions about what it is like disappear in the absence of a perceiver creating perceptions of it. BUt those perceptions are very different things from much of the rest of the world.

    IANAP, but this is how it looks to me. Cut a brain open. Is what you find there like a tree? Not at all. The probability that the world is like our perceptions of it seems to me to run close to 0/1. A tree is presumably like something (maybe it’s rough and round and vertical!), and is presumably real (if it’s real), but it isn’t anything like a human’s see-touch-smell experience of it, which occurs inside her brain and is warm, wet, and waxy.

    For me, then, the question really is, what are the criteria we have in mind for for “realness,” whether as applied to a tree or the external world more broadly? If the external world consists of a Demon’s vast warehouses of brains in vats, or if we are a computer “simulation,” – if that really turned out to be how the world is – those are still “real” external worlds, are they not? So it seems to me that when we consider realness, what we mean is whether the outside world “really is like” our perceptions of it to enough of a degree to be able to say that it’s “real” in that way. Except, again, our perceptions are real things in the world. They are parts of our brains. I feel comfortable in saying that, no, the external world is not very much like the parts of my brain where I perceive many parts of it, except in those places where the external world is no longer external to my perceptions and is instead identical to them, i.e. in those parts of my brain where they occur.

    I guess what I’m saying is that I think this problem is misconceived in important ways. Yes, the outside world is real in the sense that it has a physical reality, but it isn’t at all like our perceptions of it, which are things in the world very unlike much of the rest of it. That just seems clear to me. There are ways the world could be that we could probably argue correspond better to our perceptions than others. But I maintain the correspondence will still turn out to be really quite attenuated when you really look at it. Meanwhile there are lots of ways the world could be that would be not that much more unlike our perceptions of it than in my opinion a tree is to a human’s perception of a tree that, as it happens would conform to exactly what our ideas of what a quintessential “not-real” external world would be like. By which I mean, brain-in-a-vat scenarios. I don’t think the world consists of brains in vats (expect to the extent that it obviously does in important ways), but I actually don’t think that the ways that brain-in-vat scenarios diverge from what our perceptions of the world are is actually so importantly different for the purpose of this discussion from the way that I think the world as it actually is diverges from our perceptions of it. The world is in fact not like our perceptions of it (cut open a brain and see!). To the extent that by, “Is the external world real?” we really mean, “Is the world like our perceptions of it?,” and I think that’s to a quite great extent, then in my view there is good evidence to think the probability that it is is close to zero. Just cut open a brain and compare what you find to tree.

    So I guess I am a deep skeptic of “external world realism” as I understand what I think we really mean by it. The “external world” is wild and wacky and very much not like we experience it. I don’t think it’s nearly as loopy or controversial to say that as it might seem when we stop and think for a moment about what we really are trying to say when we try to say that the external world is “real.” If it were brains in vats, it would still be a real external world, and yet that is the scenario we contrast to that description. Whatever the brute, unperceived world really is, in my view the probabilities are that the overwhelming majority of it is hugely unlike the perceptions of it that perceivers experience – even the parts the perceivers perceive themselves to be directly perceiving. The exceptions literally are the perceptions, which are exactly like themselves.

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  2. I really think everyone is over thinking this. Any universe where induction isn’t useful is a universe that cannot support intelligent life. Without detectable pattern there can be no learning or planning for the future. There can be no mechanism at all since any mechanism depends on repeatability. Without mechanism there cannot even be life.

    A caveman can observe that the sun rises in the east and sets in the west. He has no idea why or if it will always be that way. He does not need to in order for it to be useful. It is repeatable and dependable on a time scale relevant to his life. Induction isn’t a logical principle at all. It is only pattern recognition. That’s why even unreasoning creatures can use it.

    Is the world real? I don’t even know what real means. All I know is that the utility of induction is a prerequisite for my existence. Even if I am a brain in a jar induction still works.

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    • Is the world real? I don’t even know what real means.

      I’m throwing this comment in here, since I think this is an interesting question to ask tho what follows isn’t meant to be a criticism of anything you (PPNL) have said.

      I think there’s two ways the brain in a vat can be used against realism. The first is as some sort of reduction of sensory evidence suggestive of an external world to subjective phenomenological properties. It’s not a straight reduction, it seems to me, but it leads to things like Berkely’s Idealism and the like where the only things we can know (as in justified true belief) is a Cartesian “I am” sort of thing. Or, in the empiricist’s language, a Humean perception sorta thing, where the only thing that’s real are sense data, or somesuch.

      THe other way brains in a vat are used against realism of the external world, it seems to me, is to focus attention on the methods of justification for the belief that the external world exists and demonstrate that such a belief isn’t necessary. (That is, cannot be proven via any valid argument consistent with the evidence upon which the belief could possibly be justified.)

      In either case, it seems to me that brain in a vat argument fail to establish, let alone support, the idea that either god exists or that our belief in the external world rests on faith. Those arguments fail to support god because if the entirety of our epistemic experiences are consistent with being a brain in a vat, then we are not justified in holding any beliefs beyond the sensory inputs which comprise the phenomenological properties experienced by a vat-bound brain. ANd it fails to establish that our belief in the external world rests on faith since, by hypothesis, for a brain in a vat there is no external world (at least, not one that the brain interacts with an independent agent), yet the experiencing brain will continue to act as tho an external world exists (that is, the experiencing subject will continue to be rationally justified in acting as tho his or her actions entail predictable consequences following perceived regularities).

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      • In either case, it seems to me that brain in a vat argument fail to establish, let alone support, the idea that either god exists or that our belief in the external world rests on faith

        I’m currently not interested in establishing whether God exists or not.

        ANd it fails to establish that our belief in the external world rests on faith since, by hypothesis, for a brain in a vat there is no external world (at least, not one that the brain interacts with an independent agent), yet the experiencing brain will continue to act as tho an external world exists (that is, the experiencing subject will continue to be rationally justified in acting as tho his or her actions entail predictable consequences following perceived regularities).

        You are conflating whether we are practically rational in acting as if we believed that the world we experienced was real with whether we are epistemically rational in believing it to be the case. The former can obtain without the latter being the case since, as I show above, if we our utility for phi-ing is higher than for not when the external world is real, it continues to be so even when we come to seriously doubt that the world is real. As long as we are not certain that the external world is not real (and there seems to be no reason why we should be certain that it isn’t) what practical rationality requires of us does not change. My question concerns epistemic rationality and the mere fact that a brain which is actually in a vat will likely continue to believe that it is not does not mean that it is rational to believe such.

        High levels of confidence that the world we observe is real requires faith (or at least requires us to ignore basic Bayesian calculations)

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      • You are conflating whether we are practically rational in acting as if we believed that the world we experienced was real with whether we are epistemically rational in believing it to be the case.

        I don’t think I am. I concede that the principle of induction cannot be established as a necessary principle by a deductive (or any a priori) argument. Hume established this a long time ago, no? I’m conceding that. So what am I conflating here?

        My question concerns epistemic rationality and the mere fact that a brain which is actually in a vat will likely continue to believe that it is not does not mean that it is rational to believe such.

        Depends on what you mean by “rational”, it seems to me. If you’re conception of rationality is that we’re only justified in acting on beliefs that result from a priori logic, or can be validly deduced from self-evident principles, then you’re right. But it’s a trivial, too. It’s also a reductio on drawing any inferences regarding the supposed entailments deriving from Brain in a Vat type thought experiments, since if we are brains in a vat, then absolutely nothing logically follows except for (maybe!) sense data and a Cartesian “I am”. Certainly we can’t draw any conclusions about faith in the external world since that faith is not only not justifiable, it’s flat out false – by hypothesis, there is no external world.

        What conclusions can be drawn from the BiaV? IT seems to me the only thing it establishes (assuming it’s a sound argument) is that there can be no proof demonstrating that the external world is necessary. Why think demonstrating that is necessary for individuals to be justified in believing that the sun will rise in the east tomorrow? I mean, arguing that the sun itself is illusory doesn’t refute the subjectively experienced regularity perceived by individuals regardless of whether they’re vat-brains or not.

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      • High levels of confidence that the world we observe is real requires faith (or at least requires us to ignore basic Bayesian calculations)

        See, I just don’t see how this follows. IF anything, it would require massive delusions, since if we’re brains in a vat then the thing you’re ascribing faith to (the external world) doesn’t even exist. That’s not an example of faith that something might be the case, it’s an example of a radically false belief about something that is the case. What would be the reason to conclude we’re actually brains in a vat? Certainly not merely the possibility that it’s the case. All that possibility does is establish that the external world (our conception of it, anyway) is not necessary. But from within the confines of the vat, I’m entirely justified in saying – as I just did – that the mere possibility that I’m a vat-brain doesn’t mean my belief in perceived regularities isn’t justified. All it means is that they aren’t logically necessary. But we all agree with that already. (Thanks to Hume, atually.)

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      • Btw, I can’t help but think that a careful reading of Kripkenstein clears up a bunch of the puzzles that appear when thinking about this stuff. I mean, the first section of the Investigations includes the line that when the shopkeeper receives the order for five red apples, his response is to merely “act” in accordance with certain types of rules he’s learned. That is, he’s justified in acting as he does even tho on a strict truth-conditional analysis his actions would be unjustified.

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      • The probability calculation shows that sceptical scenarios as a whole are not just possible, they are equally consistent with the available evidence and almost as likely as non-sceptical scenarios.

        Remember, given the possible worlds model of inductive and abductive reasoning, in order to establish the likelihood of a given explanation, we examine the fraction of experience consistent possible worlds that are consistent with the explanation.

        In this case, the logical possibility of systematic deception coupled with the relative lack of complexity make such scenarios sufficiently likely to warrant serious scepticism.

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      • I’m just not feeling the force of that, Murali. THe mere possibility of being a BiaV is enough for the skeptical claim to go thru. THe degree to which it’s likely that I am a brain in a vat seems irrelevant at that point, at least as far as the issues we’re talking about are concerned. But you still aren’t understanding my main point here – which is probably my fault – so I’ll try it again. THe mere possibility that we’re brains in a vat doesn’t entail faith in the external world, since if the hypothesis that we’re vat brains is true then so-called faith in the external world is definitionally incorrect. And if we’re not vat-brains, then our belief in the external world is correct and not an act of faith. The two things are just completely disconnected.

        ALsotoo, my acting as I do – which includes certain justifications for my beliefs are exactly the same regardless of whether I’m a brain in a vat or not. Eg, it’s entirely possible that the laws of logic I appeal to when making sound arguments are illusory and piped into my consciousness by evil demons at a control panel hooked up to my brain, but since I cannot reasonably conclude that such a being could exist without invoking those logical laws, I must retain my belief that using them continues to be (despite the hypothesis!) justified in the deepest sense of that word. It’s just something I cannot rationally abandon without the very argument suggesting I do so reducing to absurdity.

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      • I think you are misunderstanding me. If I were to claim that people who believe that the world they experience is real do so on faith, it would not necessarily be with any approval as a valid epistemic move.

        Moreover, the mere correctness of a belief does not preclude it being believed on the basis of faith. Consider the existence of God. Tim Kowal, to take an example, is a Catholic IIRC. It is logically possible that Jesus could appear tomorrow and say that Tim’s religious beliefs are more or less true. That would not change the epistemic status of Kowal’s beliefs today: namely that his religious beliefs are not justified by the relevant evidence and that faith, to some extent or another, underlies his beliefs. If a belief can be rational (well supported by the available evidence) but still wrong, then a belief can be irrational (not well supported by evidence) but still correct.

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  3. Any universe where induction isn’t useful is a universe that cannot support intelligent life. Without detectable pattern there can be no learning or planning for the future. There can be no mechanism at all since any mechanism depends on repeatability. Without mechanism there cannot even be life.

    How do you know this?

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    • How can you make plans in a universe where every event is independent of every other event? How can such a universe support even the mechanical functions of your body?

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      • Again:

        How do you know you have a body?

        In an absolute sense I don’t. In an absolute sense I don’t even care. Only the Sith and mathematicians deal in absolutes.

        The mistake that people make about induction is they think it is a logical principle that allows them to prove stuff. I say again it isn’t. It only detects patterns. The theories that you build from those patterns are your own. Brain in vat covers the pattern as well as anything else. Its only problem is that it contains major elements with no utility or purpose.

        If I am a brain in a vat with a computer plugged in then that is still a pattern that supports mechanism and reason. In that sense it isn’t even an argument against realism. It is only an argument that our understanding of the universe is incomplete. Well ok but we already knew that.

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  4. I think it was William Bell who described trying to understand subatomic particles as akin to trying to understand a bowling alley by rolling a ball across the lanes. Our brains are like that process — we get limited information, we misinterpret that information. It’s not the cognitive output of one that constitutes knowledge, it’s cumulative observation and re-observation thanks to our ability to communicate.

    Discussions like this always disturb me, the are extremely egocentric. But human knowledge does embrace that 1) humans are relatively new, 2) the earth is many millions of years older, and 3) the universe is many billions of years older, still. Reality happened before there were humans to observe, before we were rolling our balls at right-angles to the lanes. Reality does not require an observer; understanding reality does. It’s nice that we try to understand things, that we constantly work to understand things. I understand that sound is the air, vibrating. This is a physical thing. Sound is also the air vibrating my ear drums; so if I’m not there to hear it, is it sound? This is a game, though, just a word game. Even if I’m not there, the tree falling still vibrates the air. If there were not living things to observe it, I could still theoretically set up recording equipment to capture it. There is still he echos of that vibration re-vibrating the air.

    One of the most valuable lessons one learns from some recreational drug use — particularly hallucinogenics — is that human perception is very delicate and subject to distortion. Moldy grain, infested with rodents, and the hallucinogens so produced by that biochemistry, go a very long way to explaining the dark ages. This is a good thing to remember; reality is one thing, our perception of reality another. Just because I once experienced an apple tree embracing me does not mean that sometimes apple trees give people hugs.

    We get too caught up in observation as reality; things happen unobserved, and being unobserved, we may not know they happen, but they still happen. So there are two separate things here: what reality is, and how we observe reality. Conflating the two into a single thing is, to me, seems as silly as thinking I’m the pinnacle of evolution on a flat earth at the center of the universe

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    • But human knowledge does embrace that 1) humans are relatively new, 2) the earth is many millions of years older, and 3) the universe is many billions of years older, still. Reality happened before there were humans to observe, before we were rolling our balls at right-angles to the lanes.

      To call that knowledge, we must establish that such beliefs are at the very least justified and true. Sceptical problems reach to the heart of justification. Are our beliefs really founded on good reasons? We criticise those who justify Christianity by appealing to the Bible and in turn justify the appeal to the Bible by appealing to Christianity. Are we any better off when it comes to the “external world” or induction? Stones and glass houses and all that.

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      • Well, I don’t believe that the bible is the ‘word of God,’ I believe it’s a collection of stories by people, and that God was created by people to explain things they did not understand and create some organizing tribal social stability.

        But the real answers to your question?

        Turtles all the way down. Or 42. Take your pick; it’s nonsense no matter how you approach it. Reality does not need you or me, we’re just along for the ride, and I’m most grateful for the opportunity. What you’re discussing is what/how we perceive what’s ‘real.’ I cannot see much of the light spectrum, hear much of the sound spectrum. But that does not mean it is not there. I can’t see electrons, but I’m sure they flow though the circuits on my computer as I type. I cannot detect photons as individual things, but there is light all about me. For all these things, we’ve devised methods of observation that consistently work under specific rules. Gravity does not fluctuate, changing the rate at which my computer crashes to the floor when it slides off my lap; but I’ve seen the video images of bubbles of water floating in the space shuttle.

        For God, for gods, the proof of their existence is only in our need for explanation and order. The gods themselves are how we fill in the blanks. Inducing god vs. deducting the human need for answers seems pretty obvious to me.

        Perhaps I’m a god. Or a universe. I’m certain the flora and fauna within me think so, if they can think with their little single-celled bodies that I cannot see without aid of a microscope. They can most certainly detect food, predators and mates. And I certainly could not live without them; and that is the really important thing to induce about godhood.

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      • I’m asking how do we know that the things we perceive are real? I’m not asking whether there is anything real*. If we wish to claim the mantle of rationality, then we better be willing to scrutinise all our beliefs; even the seemingly obvious ones. Otherwise, I don’t think we are in a position to criticise others for their failure of epistemic rationality.

        *Though, since, it seems that the only thing that we know for sure is real is our own selves, it may not be clear if anything apart from ourselves is real.

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    • I’m asking how do we know that the things we perceive are real?

      And that’s exactly what I’m saying is nonsensical. That we perceive it does not make it real or unreal. Go pop some LBMs and what you’ll perceive will certainly seem real until they wear off. Seriously, I think the best answer to this question is hallucinogenic experience, which is probably why it’s so important to so many rites-of-passage into adulthood.

      Two people, or even two hundred people, can all see the same rock and see ‘rock, though there will be difference in what each perceives about rock. Two people or two hundred people on LBMs will see the same rock and each see a different thing. You might see pink elephants dancing inside it, I might see roses growing through it’s stratum. Jaybird will definitely see cats. But when the LBMs wear off, we’ll all see rock again, and we’ll have a much clearer notion of the difference between real and our perception of real, and some handle on how fragile our perception can be.

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      • I actually deal with the problems of real vs. not-real often. I get severe migraine, often optical migraine. What’s real is, sometimes, very difficult to sort out. For instance: one day, there was a car parked in front of my house, under a tree, where cars don’t normally park — that side of the street has ‘no parking’ signs on it. The sun was shining down through the leaves, and reflecting off the car. And I had migraine. For about 20 minutes, every time I looked out the window toward where the car was, my brain interpreted the light reflecting off the roof of the car as a chess board hanging in the sky. I could walk away, go back to the window, and it would still be there. The sun moved on enough that the reflection changed, and the chess board disappeared.

        Now that chess board floating in the air appeared very real to me. But I know it was a combination of light, shadow, perhaps heating air, and electrical storm in my own brain; and in fact, there was no chess board at all.

        It’s very easy to get caught up in this right up until sorting reality from brain scrambling becomes an important survival tool. And that helps one sort things out pretty quickly.

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  5. One of my professors dealt with these types of questions thusly:

    He kicked a rock.

    No, wrong professor. He said that these questions were all well and good but, at the end of the day, you still have to feed the cat. Which isn’t exactly an “I refute it thus” but you can’t help but notice that the downsides to not feeding the cat are worse than the downsides of feeding him (and the upsides to feeding him are better than the upsides to not).

    When it comes to skepticism, there are degrees beyond which it’s downright unhealthy but, more importantly, there are degrees beyond which it is obviously playing the burden of proof game where it comes up with scenarios that it’s your job to disprove rather than the other guy’s job to establish.

    There’s a level of skepticism that is downright useful (if not healthy). It’s just not waaaay over there.

    I mean, it takes one level of skepticism to say “I can’t prove my body doesn’t exist” and another to say “I can’t prove that things happened before today” and yet another to say “I can’t prove that Abraham Lincoln existed” and then yet another to say “I can’t prove that other people dream” and up and up until you get levels of skepticism where, yeah, it’s probably not only useful but entirely fair to make the other person shoulder the burden of proof.

    But it’s somewhere after Euclid.

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    • I think my last section showed that even if you are a sceptic, you still have reason to feed your possibly unreal cat. I do think that a lot of burden of justification talk is overblown and is often a cover for people who wish to heavily scrutinise others’ beliefs without applying the same level of scrutiny towards their own.

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      • I have more reason to feed him than I have reason to believe (!) that he’s possibly unreal.

        To focus on the latter as interesting once one is out of college and/or out of weed, is to make a mistake.

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      • I have more reason to feed him than I have reason to believe (!) that he’s possibly unreal.

        Exactly. Well, sorta exactly, it seems to me. The key here is in what sense we think the cat is not real, and is there any reason to think the cat’s unreality is disanalgous to my own (as the experiencing subject) or your own (as just another cat-like object in my world)? Ie., if I’m a brain in a vat, then it makes as much sense for me to fail to feed myself as it does to fail to feed the cat.

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    • “Kick a rock”; “Gotta feed the cats”; these are perfectly reasonable ways to deal with this problem from a day-to-day pragmatic standpoint. But they are both choices simply not to deal with it philosophically. They don’t resolve it, and they’re not an argument that there’s really no problem.

      Obviously we’re all going to avoid kicking rocks (barefoot at least). Is the world really “like” our perceptions of it? Is it “real” in that sense (again, if it were brains in vats, if that were real, then that would be real, but we would then say that the world isn’t “real”: that’s exactly, paradigmatically what we think about when we think about what it would be if it were “not real.”) Merely observing that we’re going to act like the world is how we perceive it doesn’t solve or address those questions; in fact it’s closer to admitting defeat by them.

      There is philosophical work that can be done (has been done) to deal with this problem strictly along pragmatic lines. But for moderns like us who want to think we know things, that line of work involves giving up huge amounts of theoretical territory we tend to be very reluctant to give up (i.e. accepting significant degrees of relativism about truth [EDIT: maybe more accurately, about knowledge] across vast swaths of inquiry).

      To pretend to deal with the problem of the real or unreal external world with “Kick a rock” without reckoning with what you have to give up if you really want to deal with the problem that way isn’t to deal with the problem. It’s just, “LALALALALALAICAN’THEARYOU.”

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      • Don’t see it as “LALALALALALAICAN’THEARYOU” as much as “sorry, the burden of proof for this being dreams in the mind of Cthulhu before he eats us is on you, it’s not on me.”

        If, however, you’d like to argue this against the Brain in a Jar folks, I’d be more than happy enough to explain how they have the burden of proof for the Cthulhu thing prior to your having it for the Brain in a Jar thing.

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      • Maybe its a good punchline, but you have to show how assigning burdens of evidence in this way actually gets you closer to the truth.

        Hint: it doesn’t. In the absence of all evidence the only appropriate default is complete agnosticism. Anything else would not apportion belief to evidence.

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      • Can we just agree that you’re using “knowledge” differently than most folks? If you’re 100% sure of a thing, like “a right angle has 90 degrees in a flat Euclidian plane”, then it’s “knowledge” and if it’s just something that comes from the senses, like “I’m married”, then it’s just something that we have to operate around as a working assumption, to be abandoned the moment we have a reason to believe that we’re in the Matrix above and beyond the deja vu that happens all the time?

        How’s this? If you want me to abandon my working assumptions, the burden of proof is on you.

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      • Jaybird,

        The brain in a vat hypothesis suffices to cast doubt on even definitional mathematical truths. It leaves nothing unscathed, which is why it’s a bit of a reductio on itsownself: if the hypothesis is true, I have no way of determining that the hypothesis even might be true.

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      • Huh, I always thought that stuff like “perfect spheres” and whatnot were left intact by the BIJ. I can always make up something, give it some traits, then say “I know that these other traits follow”.

        If nothing else, that certainly demonstrates why it’s so important to not be holding the hot potato that is the “burden of proof” when it comes time to discuss something that allows no evidence either for or against it.

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      • Can we just agree that you’re using “knowledge” differently than most folks? If you’re 100% sure of a thing, like “a right angle has 90 degrees in a flat Euclidian plane”, then it’s “knowledge”…

        That’s true by definition. I could define it differently so in what sense can this be called knowledge?

        All mathematical knowledge is arrived at by circular reasoning. You start with axioms that you do not question and derive complex proofs. But your conclusion is contained in your assumptions. That is circular reasoning. But that is how mathematical truth is defined.

        Empirical truth is defined differently but it is still a reasonable and useful definition of truth.

        In a sense mathematical truth and empirical truth are mirrors of each other. In math you start with axioms and derive complex mathematical structure. In science you start with complex empirical structure and try to derive the simple underlying axioms. In math your conclusions are absolutely true except that your reasoning is circular. In science your observations are true but your axioms are conditional and you must stand ready to abandon them.

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      • Jaybird,

        Mathematical truths are necessary, so whether we’re brains in a vat or not, from our pov as not-vat-brains those truths would hold (and necessarily) in any event. But it’s possible, gven the hypothesis of vat-brains (at least those controlled by evil demons) that the experience of deriving mathematical truth or holding mathemtical beliefs is just part of the systematic delusion. Even the belief that we’re following certain “a priori knowable” rules is subject to doubt. The rules could keep changing in each application, for example, or diverge wildly from how we currently use them without there being any mechanism to determine whether we’re drawing good inferences or not (since all of em could seem like good inferences).

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      • I don’t necessarily want you to change your views, just acknowledge that they are not fully rational. If even that counts as wanting you to change your views, then you also similarly want me to change my views. In any case, I have already provided that proof in the form of the following argument.

        P1: We should apportion belief in a proposition according to its likelihood.
        P2: Given two propositions P and ~P where both are equally consistent with the evidence but in which ~P is twice as complicated as P, the likelihood of P is 0.62
        P3: Sceptical scenarios is as consistent with the evidence as realist ones but are, in disjunction, at most twice as complicated as the corresponding disjunction of non-sceptical ones
        P4: The likelihood of the disjunct of non-sceptical scenarios is 0.62
        Conclusion: We should have 62% confidence in the proposition that the “external world is real”.

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      • What you’re missing is that I’m not trying to prove the brain-in-a-vat notion. So the burden really can’t be on me. It’s on whoever wants to prove that’s not what we are (or that it is). That’s the nature of skepticism. The burden of proof is on the one wanting to claim knowledge, that’s the very nature of what we’ve defined as knowledge. If we want to admit resemblance-to-perception external-world realism is just an assumption and we don’t know it’s true, that’s great, that’s all we’re arguing for. I’m just saying that if that’s the case it’s pretty interesting and important, even though day-to-day-wise, I’m as happy to operate on the assumption of similitude between our perceptions and the world (even despite my feeling that on barest examination that is an incoherent idea). That works fine for me for day-to-day living just like it did for your professor, but it doesn’t work fine for philosophical noodling, which I like to do. If you want to make the philosophical idea that the world might be radically different from how we perceive it go away via proof that it isn’t, then you have to supply the proof. Some of us like the fascinating uncertainty that the not knowing injects into life.

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      • First, I agree that the “kick a rock” or Moore’s “here is one hand” misses the point. That there is a possibility that there is no external world is real.

        There are real world implications of this. If we assume that our senses represent the world to us, we do not know exactly how our senses correlate with the object. This is a problem in philosophy of science.

        However, I honestly have no idea where you proved that abduction yields equal reason to believe that BiaV is as likely a mind-independent world that in some way correlates with our senses. (For those of you who are non-philosophers, Bertrand Russell wrote a very nice explanation of this intended for the layperson, where he explains why you cannot prove the external world exists, but abduction (not kidnapping, but inference to best explanation) gives reason to believe it. The first two chapters of The Problems of Philosophy. I assign it when I teach intro phil, usually.)

        – Descartes introduced the evil demon to negate mathematical truths. He first asks – what if this is all a dream? That’s the basic brain-in-a-vat question. He thinks mathematical truths would still exist. He goes one step further and assumes that someone with evil intent is actually tricking him. He thinks if that were the case, then you would have to concede mathematical truths might not survive the doubt.

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      • Rose, what are you doing spending all your time in real, sunny, concretely beautiful places like gardens? We need you here, mushrooming with us in the closet of doubt, setting us straight!

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      • I garden to escape from philosophy, and I philosophize to escape from gardens.

        Murali, it seems like you’re making a couple of mistakes. One is that epistemic possibility entails metaphysical possibility. This is part of what Kripke argues against. Second, you have a mereological problem. What is a moving part, and how on earth are we supposed to know how many parts it takes to make an evil demon? It seems as if on your account, there are no more moving parts than a world that is the same as the actual, but that I am omnipotent. Thus, it’s just as likely that I am omnipotent as not.

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      • One is that epistemic possibility entails metaphysical possibility.

        You’re right that I didn’t consider the distinction. But now that you brought it up, I’m not sure what argument could show that such sceptical scenarios are logically but not metaphysically possible. I’ll have to do some reading to bone up on my metaphysics. I’ll also have to think about which sense of possibility I care about. Since my goal is largely epistemic, I might want there to be possible worlds which may be metaphysically impossible but which are not known to be such given the set of experiences people have.

        Second, you have a mereological problem. What is a moving part, and how on earth are we supposed to know how many parts it takes to make an evil demon?

        By moving part, I mean independent premise (since possible worlds are just sets of sentences). Some premises posit independent entities. Other premises further specify the nature of such entities.

        Re

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      • Things like gravity, strong force, weak force and electromagnetism are thus (at the minimum) logical objects we posit in order to make the content of our subjective experience more probable…

        Once you posit the existence of such logical objects, the expectation that future events will look like past ones is almost trivial… This solves the old problem of induction.

        Since Rose brought up abduction, I imagine you can see the problem with this part, too.

        Any story about a grue object would have to posit some such intervening cause in order to spell out what a grue object would be.

        And the problem above should illuminate the problem here. Also.

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      • since possible worlds are just sets of sentences

        If this is one of your premises, I’m definitely not on board.

        Anyhow, again, even if it were true that possible worlds were sets of sentences, the possible world in which “Rose is a philosophy professor” has as many sentences as “Rose is a chimp on roller skates.”

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      • In a sense mathematical truth and empirical truth are mirrors of each other. In math you start with axioms and derive complex mathematical structure. In science you start with complex empirical structure and try to derive the simple underlying axioms. In math your conclusions are absolutely true except that your reasoning is circular. In science your observations are true but your axioms are conditional and you must stand ready to abandon them.

        I totally agree with this and, for some reason, I have this categorized in the stuff that Plato was talking about. He saw mathematical truths as purer than the messy stuff our fingers are capable of drawing or nature is capable of making. It’s not, and will never be, a circle. Just an approximation… ah, but we can see the Form of the circle in our mind’s eye, can’t we? Scientific truths are stuck with how this circle is really a crappy oblong.

        He thinks if that were the case, then you would have to concede mathematical truths might not survive the doubt.

        Well, at this point, the game is given away. “Assume we have a system that is untestable even in theory. Now prove that we aren’t in this system.”

        “By definition, you can’t.”

        “HA! I WIN!”

        At that point, well… you’re stuck watching your interlocutor enjoying his spoils and now you have to feed the cat.

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      • Murali,

        Since my goal is largely epistemic, I might want there to be possible worlds which may be metaphysically impossible but which are not known to be such given the set of experiences people have.

        I don’t mean this question to sound condescending but have you read Kripke on this stuff? In Naming and Necessity he talks quite about what he refers to as “qualitatively identical epistemic situations” as a way of teasing out some problems in the conceivability entails possibility line of reasoning. (There’s also a ton of secondary stuff on what that rephrasal technique means for possible worlds and the mind-body problem, etc.) Also, have you read any of Chalmer’s stuff on two dimensional semantics which tries to provide an analysis of meaning across two contexts, specifically modal contexts. His work is basically a lift from Stalnaker’s and Kaplan’s previous arguments, and even tho he basically made his entire career by pretty much repeating and systematizing what they were getting on about it’s a pretty good read.

        I’m not sure these writers will help you fill out your argument, but there is some pretty good stuff on conceivability (and what that entails) and possibility, and in what sense conceivability entails possibility.

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      • Agree with Stillwater about Kripke. Also, there was a book that came out about 10 years ago called “Conceivability and Possibility” ed by Gendler and Hawthorne. The intro is a really really good overview of the issue. I found it really helpful orienting myself. Since my dissertation was on emotional responses to fictions, I had to dip a little into this stuff, since whatever a fictional character turns out to be has some bearing. (Although I don’t think it contains anything about 2D semantics…that stuff came out after, maybe…or maybe I misremember)? http://www.amazon.com/Conceivability-Possibility-Tamar-Szabo-Gendler/dp/0198250908/ref=sr_1_1?ie=UTF8&qid=1402929352&sr=8-1&keywords=conceivability+and+possibility

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      • Also, some of the essays in the book are really good. Unfortunately Greg Currie, of whom I’m usually a fan, has an essay in the book on imaginative resistance which is not his best. (Imaginative resistance is a topic I wrote on).

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      • It’s extremely unlikely that Rose the rollerskating chimp would type wonderful posts on gardening and philosophy. Given that I experience reading her posts, if Rose exists, she is almost certainly not a rollerskating chimp

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      • It’s extremely unlikely that Rose the rollerskating chimp would type wonderful posts on gardening and philosophy. Given that I experience reading her posts, if Rose exists, she is almost certainly not a rollerskating chimp

        Right. And it seems quite unlikely given the way the world is that there is not a mind-independent reality. Abduction.

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      • But, the rollerskating chimp hypothesis is one that entails that I would have different experiences than the one I think I have been having while the evil demon and brain in vat hypotheses are constructed to entail that I have the same experiences I think I have had.

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  6. Perhaps I’m in way over my head, but:

    I’m reading Anthony Kenny’s History of Western Philosophy, nearly at the end of Book I.

    And while I realize my take is probably not an educated take, but it seems to me that the whole reason Aristotle kicked butt is that he understood the importance of leaving the ivory tower, getting out of his own head, and going out and talking to the experts who gained expertise through doing — to the weavers, the potters, the fence builders, the farmers, the cooks.

    There is some level of hubris in thinking one can understand reality without actually going out and engaging reality. Logically, it’s prey to the problem of thinking things that are fractal are linear (always a problem for the human mind; like thinking one is an individual instead of recognizing that each individual human is a complex web of living organisms, and the health of the individual rests on the health of that web).

    It’s very easy to look at a watershed and think the major river through it the thing of importance in the watershe; but it’s the fingerling trickles of water that make that river. The quality of the water in the watershed rests not on the quality of the river first, but on the health of those small, often ephemeral trickles that feed the river. You can never understand the river if you don’t understand the feeder streams, too.

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  7. We thus don’t have to assume that the external world is real in order to do science or go about our daily lives. At most, we just have to acknowledge some possibility that the world we observe is real as far as daily practical problems are concerned. On the theoretical end, we just have to be careful and be modest about the claims that we can make. However, as we have seen, this does not invalidate our current scientific knowledge.

    Navel-gazing at its finest.

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