The Fabric of Real Things
Followup to: The Useful Concept of Truth
We previously asked:
What rule would restrict our beliefs to just statements that can be meaningful, without excluding a priori anything that could in principle be true?
It doesn't work to require that the belief's truth or falsity make a sensory difference. It's true, but not testable, to say that a spaceship going over the cosmological horizon of an expanding universe does not suddenly blink out of existence. It's meaningful and false, rather than meaningless, to say that on March 22nd, 2003, the particles in the center of the Sun spontaneously arranged themselves into a short-lived chocolate cake. This statement's truth or falsity has no consequences we'll ever be able to test experientally. Nonetheless, it legitimately describes a way reality could be, but isn't; the atoms in our universe could've been arranged like that on March 22nd 2003, but they weren't.
You can't say that there has to be some way to arrange the atoms in the universe so as to make the claim true or alternatively false. Then the theory of quantum mechanics is a priori meaningless, because there's no way to arrange atoms to make it true. And if you try to substitute quantum fields instead, well, what if they discover something else tomorrow? And is it meaningless -rather than meaningful and false - to imagine that physicists are lying about quantum mechanics in a grand organized conspiracy?
Since claims are rendered true or false by how-the-universe-is, the question "What claims can be meaningful?" implies the question "What sort of reality can exist for our statements to correspond to?"
If you rephrase it this way, the question probably sounds completely fruitless and pointless, the sort of thing that a philosopher would ponder for years before producing a long, incomprehensible book that would be studied by future generations of unhappy students while being of no conceivable interest to anyone with a real job.
But while deep philosophical dilemmas such as these are never settled by philosophers, they are sometimes settled by people working on a related practical problem which happens to intersect the dilemma. There are a lot of people who think I'm being too harsh on philosophers when I express skepticism about mainstream philosophy; but in this case, at least, history clearly bears out the point. Philosophers have been discussing the nature of reality for literal millennia... and yet the people who first delineated and formalized a critical hint about the nature of reality, the people who first discovered what sort of things seem to be real,were trying to solve a completely different-sounding question.
They were trying to figure out whether you can tell the direction of cause and effect from survey data.
Please now read Causal Diagrams and Causal Models, which was modularized out so that it could act as a standalone introduction. This post involves some simple math, but causality is so basic to key future posts that it's pretty important to get at least some grasp on the math involved. Once you are finished reading, continue with the rest of this post.
Okay, now suppose someone were to claim the following:
"A universe is a connected fabric of causes and effects."
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vs. |
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(In the right-hand image we see a connected causal fabric; the sun raises the temperature, makes plants grow, and sends light into the eyes of the person eating from the plant. On the other hand, while "post-utopian" is linked to "colonial alienation" and vice versa, these two elements don't connect to the rest of the causal fabric - so that must not be a universe.)
This same someone might further claim:
"For a statement to be comparable to your universe, so that it can be true or alternatively false, it must talk about stuff you can find in relation to yourself by tracing out causal links."
To clarify the second claim, the idea here is that reference can trace causal links forwards or backwards. If a spaceship goes over the cosmological horizon, it may not cause anything else to happen to you after that. But you could still say, 'I saw the space shipyard - it affected my eyes - and the shipyard building was the cause of that ship existing and going over the horizon.' You know the second causal link exists, because you've previously observed the general law implementing links of that type - previously observed that objects continue to exist and do not violate Conservation of Energy by spontaneously vanishing.
And now I present three meditations, whose answers (or at least, what I think are the answers) will appear at later points in Highly Advanced Epistemology 101 For Beginners. Please take a shot at whispering the answers to yourself; or if you're bold enough to go on record, comments for collecting posted answers are linked.
"You say that a universe is a connected fabric of causes and effects. Well, that's a very Western viewpoint - that it's all about mechanistic, deterministic stuff. I agree that anything else is outside the realm of science, but it can still be real, you know. My cousin is psychic - if you draw a card from his deck of cards, he can tell you the name of your card before he looks at it. There's no mechanism for it - it's not a causal thing that scientists could study - he just does it. Same thing when I commune on a deep level with the entire universe in order to realize that my partner truly loves me. I agree that purely spiritual phenomena are outside the realm of causal processes, which can be scientifically understood, but I don't agree that they can't be real."
How would you reply?
"Does your rule there forbid epiphenomenalist theories of consciousness - that consciousness is caused by neurons, but doesn't affect those neurons in turn? The classic argument for epiphenomenal consciousness has always been that we can imagine a universe in which all the atoms are in the same place and people behave exactly the same way, but there's nobody home - no awareness, no consciousness, inside the brain. The usual effect of the brain generating consciousness is missing, but consciousness doesn't cause anything else in turn - it's just a passive awareness - and so from the outside the universe looks the same. Now, I'm not so much interested in whether you think epiphenomenal theories of consciousness are true or false - rather, I want to know if you think they're impossible or meaningless a priori based on your rules."
How would you reply?
Does the idea that everything is made of causes and effects meaningfully constrain experience? Can you coherently say how reality might look, if our universe did not have the kind of structure that appears in a causal model?
Part of the sequence Highly Advanced Epistemology 101 for Beginners
Next post: "Causal Diagrams and Causal Models"
Previous post: "Firewalling the Optimal from the Rational"


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Comments (305)
I feel that it would be meaningful to claim that there are actually other universes which don't causally interact with ours, although (like the claim about photons disappearing when they are sufficiently far away from us) it would not be testable. This seems to be a counterexample to the causal connection requirement. [A good scientific theory would posit a common cause for these universes, but that is beside the point: it seems conceivable that they have no common cause.]
As such, I'm tempted to claim that what is real is just what actually is. There isn't an internal criteria for determining that, such as causal connectedness.
(This does not force any particular position about what is meaningful.)
It's worth mentioning that the first people to rigorously apply Bayes net methods to causal discovery (as far as I know; correct me if I'm wrong) were philosophers. They were the ones who formulated the causal Markov principle. Also, a precursor to the CMC was formulated over half a century ago by another philosopher, Hans Reichenbach. It is true that work of this sort is unrepresentative of what goes on in most philosophy departments (although it's not all that unrepresentative of what contemporary philosophers of science are doing), but as someone who would like to see a lot more of this kind of philosophy, it annoys me a little when this work isn't acknowledged as philosophy done by philosophers.
You should give some credit to the logical positivists, because you seem to be trying to re-invent logical positivism. It would be nice to explain how what you're getting into differs from logical positivism.
It would also be nice to do a critical analysis of the refutation of logical positivism. Students today are taught that it's completely discredited. But it was "disproved" by philosophers, which should give one pause. Quine's "proofs" of the principle of ontological relativity, at least, are completely vacuous; and if you do the math, you find that it's false.
This example has been used by Eliezer before in the Sequences, and it is a bit problematic under the latest physical theories. Assuming cosmological horizons behave like black hole event horizons, the theories say the following:
Accordingly, anyone taking a trip on that spaceship shouldn't be at all confident they'll reach anywhere!
But there is an interesting (and rather worrying) follow-through to this reasoning. In cosmology, we observe something very like a positive cosmological constant (lambda term) pushing galaxies apart at an accelerating rate. If it continues to behave like a cosmological constant, then every galaxy in the universe is exactly like the spaceship, and will eventually red-shift into a cosmological horizon with respect to every other galaxy. It apparently follows from this that every galaxy in the universe (including our own) can only continue to exist for a finite proper time before getting scrambled into Hawking radiation. So we're not actually any safer staying on Earth than going off in the spaceship! This "end-of-time" effect has been discussed in a number of recent papers including this one by Raphael Bousso: the predicted end is in about 5 billion years. Needless to say, the effect is extremely controversial, as is the chain of reasoning leading to it. But if there is something wrong with the reasoning, it's not clear where...
Why on Earth would they?
Edit: Also that paper does not say anything about cosmological horizons converting anything into Hawking radiation! It's an entirely different and stranger argument.
In asymptotically flat spacetimes, the event horizon of a black hole is defined (roughly) as the boundary of the region of spacetime that can be seen by an immortal observer (more precisely, it's the boundary of the causal past of future null infinity). If you extend this definition to generic spacetimes, then it applies to the cosmological event horizon in a spacetime with positive cosmological constant. Because of this formal similarity, a number of results in black hole thermodynamics (specifically, the laws of black hole mechanics) can be generalized to the cosmological horizon.
Anyway, one response (Susskind's) to the sort of thing drnickbone brings up, in the case of black holes, is black hole complementarity. We seem to have this paradox when something falls into a black hole. On the one hand, we don't want information to disappear beyond the event horizon, so the information must be absorbed into the event horizon itself, theoretically readable off the structure of the horizon (or off Hawking radiation). On the other hand, from the perspective of an infalling observer, nothing special happens as she passes through the horizon. It certainly doesn't seem to her as if the information she carries has been smeared over the event horizon. Susskind's response is essentially that both of these things happen. The information is both reflected and transmitted by the event horizon. But the no-cloning theorem rules out the possibility that the reflected and transmitted information are two separate things. Instead, they are the same event described from different perspectives.
From an outside observer's perspective, the information is painted onto the horizon. From an infalling observer's perspective, the information passes right through the horizon. Extending this idea to the cosmological horizon and a spaceship leaving my horizon: From the perspective of the spaceship nothing special has happened. After all, why should they care about my horizon. From my perspective, once the spaceship hits the horizon, all the information constituting the spaceship is now smeared over the horizon. And of course, if I am to abide by the no-cloning theorem, I cannot simultaneously maintain that the spaceship continues to travel past the horizon. From my perspective, the spaceship does cease to exist (except as information encoded in the structure of the 2-dimensional cosmological horizon).
[ETA: I should have mentioned that this isn't just completely baseless speculation on Susskind's part. He bases his claim on an argument from string theory. The basic idea is this: The spatial extent of a string's wave function depends on the "resolution time", which is the time scale over which observations are made. As this time scale gets smaller and smaller, i.e. as our observations get faster, the spatial extent of the string gets larger. As long as the resolution time is significantly larger than the Planck time, the effect of this phenomenon is negligible. Now think of someone falling into a black hole while making measurements on a string. Another observer is outside the black hole looking on. The infalling observer's resolution time won't change as she falls. But the outside observer's resolution time will effectively get smaller and smaller, due to gravitational time dilation. As a consequence, the string gets bigger and bigger from his perspective. As the falling observer hits the event horizon, the string is big enough to be spread across the entire horizon, which means the information it contains is now spread across the event horizon. So from the outside observer's perspective, the string never falls into the black hole; it gets smeared across the horizon and the information is eventually radiated out. And since the infalling observer is also made of strings, she unfortunately gets spread across the horizon too. But none of this holds in the infalling observer's perspective. The string doesn't grow in size -- it remains localized and falls through the event horizon into the singularity. So, very speculative, but not baselessly so.]
An update. I didn't realise this a couple of months ago, but it seems there has been a big controversy brewing recently about black hole complementarity, and whether it is consistent. There was a key paper by Polchinski and three others in August Complementarity or Firewalls?; see also his guest post in Discover.
The basic argument is that there is a new black hole paradox: quantum states on the edge of a horizon have to be fully entangled BOTH with Hawking radiation that has already emerged from the black hole AND with neighbouring states that are just inside the black hole. And that is not possible, because there is a "monogamy" of quantum entanglement. Further, complementarity doesn't help, because an observer could in principle collect the entangled radiation that had already emerged from the black hole, distill it, and then bring it into the black hole to meet its duplicate entangled state inside, which would lead to quantum cloning. Oops. Instead Polchinksi et al propose that there is a "firewall" at the black hole event horizon which would destroy the second entanglement, and also destroy any observers going into the black hole.
There seems to have been a big fight on the high energy physics archive, with lots of authors drafting papers in an attempt to refute Polchinski et al, then withdrawing them or heavily editing them. Bousso also had a go, claiming that they had misunderstood complementarity, then retracted; his latest version argues that they've found a genuine paradox after all.
To be fair, not many of these physicists/cosmologists agree with the firewall solution, probably because it can leads to observers suddenly disappearing into flame without warning (it is possible to reach an event horizon around a very large black hole in otherwise normal space, with no outward-sign that is coming, then smash into the firewall and die). That violates the same sorts of physical intuitions that Eliezer raises in the main article (and which I challenged). It's also not clear exactly when a firewall forms (if it does) or if there are firewalls at cosmological horizons.
Worth watching for more developments.
P.S. I found the following interesting paragraph in Bousso et al which considers Susskind's complementarity proposal. It seems to make a big difference whether you define an observer first (and then consider his causal horizon), or define a causal patch first (together with its horizon) and then consider where the observer might be:
If we consider it in "many worlds" terms, then the wave function over the causal patch contains many different branches, and human observers (indeed our whole Milky Way galaxy) get to exist in lots of those branches. But in only a very few of the branches is our galaxy near the centre of the patch and able to continue to survive for 100s of billions of years; in most of the other branches we are somewhere off-centre, and will be smeared out against the horizon very much sooner. The fact that the Milky Way will continue to exist in some branches does not mean we should expect to survive in our branch. This reminds me somewhat of the discussions on quantum suicide.
Thanks for this, though in a way, Susskind's interpretation seems to be even weirder than that of Bousso et al.
In Susskind's view, we would have to say that every galaxy apart from ours has an end-of-time experience, and gets smeared out on the horizon (or thermalized by de Sitter radiation), still in an average of about 5 billion years. But our own doesn't... so in 100 billion years or so we will be the lucky sole survivors in a universe containing a single remaining galaxy. Yet we are not really "lucky" because every other galaxy is experiencing the same thing from its own galacto-centric viewpoint. And while these individual amazing survivor stories are all consistent, there is no globally consistent story where all the galaxies continue to survive, just moving further and further apart. Strange...
Because they're both horizons, of course!
That question sprung to mind too, right before "How could that even make sense?" and a few hundred milliseconds later "What are the precise engineering details required for me to use this effect (and the implied possibility for FTL communication) to go back and sink the first fleet, thereby preventing my own existence?".
(My reply is to the version conveyed within the grandparent, not to the strange argument. It is probably best for me to hold off reading said strange argument until is confirmed as reasonable by a sufficiently trusted source. Given the complexity of the subject I may forget to not-believe something I read.)
Well there's nothing in the Gibbons-Hawking effect (all causal horizons have a temperature and emit thermal radiation), or in the referenced paper of Bousso et al to imply FTL travel. Where did you get that idea? The "end-of-time" papers may be wrong but they're not that wrong...
Well horizons might not behave exactly the same (this is all theoretical physics) but there is quite a long chain of papers arguing that Hawking radiation arises from all sorts of causal horizons, and for the same sorts of reasons that motivate it for black hole horizons. See Gibbons-Hawking effect or look up "de Sitter radiation" on Google scholar. Here's just one paper.
With regard to your edit, the paper by Bousso et al does in fact discuss physical interpretations of the "end of time" effect, and scrambling into radiation appears to be the authors' preferred interpretation. See Section 5.3 on "causal patch measure" and this paragraph:
Is there some reason this article hasn't been promoted to the frontpage?
I actually think this a confusing statement. From a thermodynamic perspective, it's not impossible that the particles in the center of the Sun spontaneously arranged themselves into a short-lived chocolate cake on that day. It's very, very, extremely unlikely, but not actually completely impossible.
The extreme unlikelihood (roughly equal to me temporarily becoming a chocolate cake myself) is such that we are justified, in terms of the approximation that is plain English, in saying that it is impossible that such a thing occurred, and that it is just wrong to claim that it happened. But this is using the usual rule of thumb that absolute truth and falsity isn't something we can actually have, so we happily settle for saying something is true or false when we're merely extremely sure rather than in possession of absolute proof.
It's quite OK in that context to claim that it's meaningless and false to claim that the chocolate cake appeared, as the claimant has no good reason to make the claim, and saying the claim is false is pointing out the lack of that reason. The bit I don't agree with is your final sentence.
Here's where it gets confusing. If you are speaking in colloquial English, it's true to say that it's impossible that a chocolate cake could appear in the middle of the Sun, and therefore it didn't happen. If you're speaking more scientifically, it's instead true to say that it's possible that the atoms in the Sun's core could spontaneously form a chocolate cake, but the likelihood is of the order of 10^10^23 (or something like that) against, which clearly is sufficiently close to impossible for us to say informally that it didn't happen. As the sentence stands, you end up making a claim of knowledge which you don't have - that it was possible that a certain state of affairs could occur in the Sun, but that you know somehow that it didn't.
More generally, Eliezer takes an explicit and very detail oriented approach to some aspects of some topics, but takes a very informal and relaxed approach to other topics. It seems to me that he pays attention to detail more when he agrees with the arguments he is outlining. This has the effect of making the arguments he opposes seem artificially weaker.
This isn't directly relevant to the chocolate cake issue, but your comment reminded me of this.
I agree - I think this is because Eliezer's intent is to explain what he believes to be right, rather than to worry too much about the arguments of those he doesn't agree with. An approach I entirely agree with - my experience is that debate is remarkably ineffective as a means of reaching new knowledge, whilst teaching the particular viewpoint you hold is normally much more enlightening to the listener, whether they agree with the viewpoint or not.
3) If causes and effects do not meaningfully constrain experience, the universe could look like literally anything from moment to moment, regardless of what it was a moment ago. If that were the case, it is certain that the universe would enter every possible state given enough 'time'- even the state where you are reading a comment on the internet with a memory of sensory perception of a consistent world.
Could something else constrain experience, even if causes and effects didn't?
There is nothing which could have the effect of constraining the universe without causation. It is possible that experience is constrained without a cause for that constraint.
What could possibly have the effect of constraining experience in the general absence of causality?
This is what I was trying to get at.
However, without causation, the constraints on experience (or the fact that experience was constrained) would have no effect.
I have to ask, how does this metaphysics (cause that's what it is) account for mathematical truths? What causal models do those represent?
My bad:
Someone already asked this more cleverly than I did.
I have a plausibly equivalent (or at least implies Ey's) candidate for the fabric of real things, i.e., the space of hypotheses which could in principle be true, i.e., the space of beliefs which have sense:
A Hypothesis has nonzero probability, iff it's computable or semi computable.
It's rather obviously inspired by Solomonoff abduction, and is a sound principle for any being attempting to approximate the universal prior.
What if the universe permits hyper-computation?
Hmm, it depends on whether or not you can give finite complete descriptions of those algorithms, if so, I don't see the problem with just tagging them on. If you can give finite descriptions of the algorithm, then its komologorov complexity will be finite, and the prior: 2^-k(h) will still give nonzero probabilities to hyper environments.
If there are no such finite complete descriptions, then I gotta go back to the drawing board, cause the universe could totally allow hyper computations.
On a side note, where should I go to read more about hyper-computation?
If I really want to, there's an easy way for me to sidestep this. I just postulate something called "post-consciousness" which is caused both by colonial alienation and by particular arrangements of neurons in the brains of particular people (in a similar way to that in which epiphenomenalists would say consciousness is caused). Presto! A causal chain from my familiar causal fabric to colonial alienation.
In fact, we can add an extra node to any causal diagram without affecting the probabilities of observations only involving the other nodes, by making it an effect of all other nodes but not a cause of anything. By so doing we can connect the diagram up. Thus although we can't subvert the approach in Eliezer's post by postulating an ultimate cause (God), we can always subvert it by postulating an ultimate effect.
What I have said isn't normally a problem in real-life applications of the test `is it part of this connected causal fabric', since very often no such causal connection is postulated. My point is that this test can't in-principle rule out anything. It can only serve as an in-practice test by which we can temporarily rule out objects for which no such causal connection has been postulated.
I think it makes more sense to say that this test rules out ideas that can't actually be tested as hypotheses. An idea can only be tested by observation once it is formulated as a causal network. Once it's formulated as a testable hypothesis, you can simply discard this epiphenomenal example by Solomonoff induction.
Koan 4: How well do mathematical truths fit into this rule of defining what sort of things can be meaningful?
Mathematics is a mental construct created to reliably manipulate abstract concepts. You can describe mathematical statements as elements of the mental models of intelligent beings. A mathematical statement can be considered "true" if, when an intelligent beings use the statement in their reasoning, their predictive power increases. Thus, " '4+4=8' is true" implies statements like "jslocum's model of arithmetic predicts that '4+4=8', which causes him to correctly predict that if he adds four carrots to his basket of four potatoes, he'll have eight vegetables in his basket"
I'm no sure that "use the statement in their reasoning" and "their predictive power increases" are well formed concepts, though, so this might need some refining.
Most mathematics has isomorphism to typographical or computational rules. I'm pretty sure these can be encoded into a causal diagram which connects with the real world.
Do you mean that some of those strings are useful in modeling the "real world"? Say, by providing a way to discover further causal diagrams?
Not necessarily. I've realized I'm more confused than I thought I was.
I find mathematics most about future physics laws who will be discovered. Math without empirical confirmation is more difficult to link, but normally is a matter of time to find a application.
Hrm?
You think some future experimental results will say something meaningful about whether mathematics should accept the axiom of choice? Even if the universe is inconsistent with ZFC, why does that imply studying ZFC based mathematics should stop?
This seems especially difficult noting that although we can claim that things are caused by certain mathematical truths, it doesn't really make sense to include them in our Bayesian net unless we could say, for example, how anything else would be different if 2+2=3.
What sort of things?
Well I know that when I drop something the distance it falls after time t is roughly 1/2 g t^2 where g~10 m/s^2. When I drop something off of a 20m high building, I can reasonably claim that the fact that it takes roughly 2s to reach the ground is a consequence of the above, and of the mathematical truth that 1/2 * 10 * 2^2 = 20.
That's a physcial truth, and a local one at that. The mathematical expression of a physcial fact is not a "mathematocal truth" because, pace Tegmark, most mathematical truths don't model physical facts. What casues objects to fall is gravity. Maths does not cause it, any more than words do.
An event can have more than one cause. My uncertainty about the value of some variable in an equation is related to my uncertainty about the outcome of an experiment in exactly the way that makes Pearlean methods tell me that both the value of t in the equation and the physical truth that g ≈ 10 m/s^2 are causes of the amount of time that the object takes to fall. This is just a fact about my state of uncertainty that falls directly out of the math.
"Falls out of the math" doens't mean "caused by math" any more than "expressed in math" means "caused by math".
Sorry, I was unclear. I meant that the causal structure where the equations of physics cause the outcome of the experiment falls out of the Pearlean causal math, not that the outcome of the experiment falls out of the physical math (though the latter is of course also true).
I think that still has the same problem. The (edit:) math is the map, causes are in the territtory.
I'm not sure what you mean. Pearlean causality, as I understand it, is about maps. You put in a subjective probability distribution and a few assumptions and a causal structure comes out.
I agree that mathematical truths do not have effects on their own. But when combined with mathematical formulations of laws of reality they do have observable consequences. The timing of a falling projectile above is a consequence of both a mathematical formulation of the law of gravity and a purely mathematical arithmetical fact. If you somehow want to describe the universe without mathematics, good luck.
I am confused by these posts. On one hand, Eliezer argues for an account of causality in terms of probability, which as we know are subjective degrees of belief. So we should be able to read off whether X thinks A causes B from looking at conditional probabilities in X's map.
But on the other hand, he suggests (not completely sure this is his view from the article) that the universe is actually made of cause and effect. I would think that the former argument instead suggests causality is "subjectively objective". Just as with probability, causality is fundamentally an epistemic relation between me and the universe, despite the fact that there can be widespread agreement on whether A causes B. Of course, I can't avoid cancer by deciding "smoking doesn't cause cancer", just as I can't win the lottery by deciding that my probability of winning it is .9.
For instance, how would an omniscient agent decide if A causes B according Eliezer's account of Pearl? I don't think they would be able to, except maybe in cases where they could count frequencies as a substitute for using probabilities.
OK, let's say you're looking down at a full printout of a block universe. Every physical fact for all times specified. Then let's say you do Solomonoff induction on that printout -- find the shortest program that will print it out. Then for every physical fact in your printout, you can find the nearest register in your program it was printed out of. And then you can imagine causal surgery -- what happens to your program if cosmic rays change that register at that moment in the run. That gives you a way to construe counterfactuals, from which you can get causality.
ETA: There's still some degrees of freedom in how this gets construed though. Like, what if the printout I'm compressing has all its info time-reversed -- it starts out with details about what we'd call the future, then the present, then the past. Then I'd imagine that the shortest program that'd print that out would process everything forward, store it in an accumulator, then run a reversal on that accumulator to print it out, the problem being that the registers printed out from might be downstream from where the value was. It seems like you need some extra magic to be sure of what you mean by "pretend this fact here had gone the other way"
This question seems decision-theory complete. If you can reify causal graphs in situations where you're in no state of uncertainty, then you should be able to reify them to questions like "what is the output of this computation here" and you can properly specify a wins-at-Newcomb's-problem decision theory.
An omniscient agent would have no reason to decide if A causes B, since causality is a tool for predicting the outcomes of interventions, and the omniscient agent already knows what's going to happen. The concept of "causality" is only useful from a perspective of limited knowledge, much like probability. And the concept of an "intervention" only makes sense in a level of abstraction where free will is apparent.
Pearl addresses this in slide 47 of this lecture. Causality disappears if you consider the entire universe as your object of investigation.
I think Bundle's question is just that, given the above, how can Eliezer also say that the universe is actually made of cause and effect?
Does Eliezer say that the universe is actually made of cause and effect? Also, what work is "actually" doing in that sentence?
"Actually" isn't intended in any sense except emphasis and to express that Eliezer's view is contrary to my expectations (for instance, "I thought it was a worm, but it was actually a small snake").
Eliezer does seem to be endorsing the statement that "everything is made of causes and effects", but I am unsure of his exact position. The maximalist interpretation of this would be, "in the correct complete theory of everything, I expect that causation will be basic, one of the things to which other laws are reduced. It will not be the case that causation is explained in terms of laws that make no mention of causation". This view I strongly disagree with, not least because I generally think something has gone wrong with one's philosophy if it predicts something about fundamental physics (like Kant's a priori deduction that the universe is Euclidean).
I suspect this is not Eliezer's position, though I am unsure because of his "Timeless Physics" post, which I disagree with (as I lean towards four-dimensionalism) but which seems consonant with the above position in that both are consistent with time being non-fundamental. If he means something weaker, though, I don't know what it is.
Yes, I think Timeless Physics puts you on the right track, and it should be pretty clear that "causality" doesn't apply so much at the level of comparing possible states of configuration space, aside from perhaps metaphorically to point to which ones are adjacent to which other ones.
Well, if I may take up Bundle's question on his behalf, Eliezer said, in the article to which these are comments:
and
Where I take the second quote to imply an endorsement on Eliezer's part of the claim 'everything is made of causes and effects'.
I don't know, I was quoting (without making that clear) Bundle's phrase.
That was from a koan, and a good one at that. How would one perform an experiment to determine whether the universe operates on causes and effects? It suggests there might be something wrong with the conception that the universe is "made of" causes and effects.
Maybe, though given the introduction to the article, I think the koan is about the question 'what counts as meaningful?', not 'is the universe made of causal relations'.
But, perhaps more interesting than settling the question of whether or not Eliezer thinks the universe is made of causal relations, we can ask "Is the thesis that the universe is made of causal relations inconsistant with Eliezer's (and your) views on the objectivity of causal relations?'
Given your responses, my dialectical instincts are telling me you think the answer to the above is 'Yes, they are inconsistant, and it is false that the universe is made of causal relations'. Is that so?
Yes. I thought I actually made that explicit. At least, it's not "made of" causal relations any more than it's "made of" probability.
Thanks. I think Eliezer is endorsing the 'causal relations are fundamental' reading, and that this apparently conflicts with the idea that causality is the tool of a limited observer. I think he's likely to see these as reconcilable in some way. That, at any rate, is my prediction.
My prediction is that he never noticed this problem before.
Indeed. Eliezer motivates causal graphs by pointing to limitations in the observer: It's just not feasible to gather all of the necessary frequencies to do pure Bayesian conditionalization. But that's saying something about the observer, not about the object that the observer is talking about.
We're only talking about causal networks because of our own limitations as epistemic agents. It seems a weird leap to say that reality itself is made out of this stuff (causal networks) that we wouldn't even be thinking about if it weren't for our own imperfections.
An omniscient agent could still describe a causal structure over the universe- it would simply be deterministic (which is a special case of a probabilistic causal structure). For instance, consider a being that knew all the worldlines of all particles in the universe. It could deduce a causal structure by re-describing these worldlines as a particular solution to a local differential equation. The key difference between causal vs. acausal descriptions is whether or not they are local.
It seems to me that this is the primary thing that we should be working on. If probability is subjective, and causality reduces to probability, then isn't causality subjective, i.e., a function of background knowledge?
This seems not in the least contentious, if you're talking about the map of causality.
The question is whether causality exists in the territory at all.
Thanks for succinctly articulating what was bothering me about this post. Can't upvote this enough.
But if you're talking about the entire universe, then there aren't any causes and effects, just as there isn't any time. Causality only shows up when you look at a slice of the system, and whether A causes B or B causes A or they are actually independent can vary based on which slice you choose.
I like this post a lot, even though it's short (or, er, bipartite). It covers the stuff it needs to.
In fact, I'd prefer for it to be 2 posts: one before "Causal Diagrams and Causal Models" in the sequence, one after.
Agreed. The paragraph instructing me to drop what I'm doing and go read some other post, felt quite jarring.
Koan 3:
Does the idea that everything is made of causes and effects meaningfully constrain experience? Can you coherently say how reality might look, if our universe did not have the kind of structure that appears in a causal model?
Does EY give his own answer to this elsewhere?
Try to guess what he would say before reading it. You can also click on one of the tags above to read, say, the sequence on epistemology.
Meditation 3: [Hardest of the meditations, for me.] Let us observe the difference between [post-utopian]-->[colonial alienation] and a connected thing (say [I see you picked Ace]-->[You see you picked Ace] from a deck of cards): In the first case, there is no way to settle an argument about whether Ellie is post-utopian or not. We would predict that it would cause arguments between people that are not settled. Anything connected to the causal web is more likely to lead to settlable arguments, at least among people behaving more-or-less rationally. It is not a perfect test, but it does suggest that I expect to see different things from connected networks and unconnected networks, like people changing their minds.
There are three alternatives I can think of:
1) The universe has a joint probability distribution such that events are not independent, but so few events are independent that limiting the description to a causal one does not materially reduce the complexity of the "true" model. In this case, There would only be the joint look-up table.
2) All events are independent.
3) The universe is not well-described by the laws of probability.
The first case would make prediction pretty much impossible (since you're never dealing with the exact same set of variables twice). "Same river" and all that. No prediction more specific than "the universe persists in some way" would be true very often on average, since there are so many possible outcomes, and no reason to believe that the next joint probability for the event you care about is similar to the last one.
In the second, you could predict roughly the proportion of events based on the proportion of past events, but there would be no discernible pattern, or result of action.
In the third, I can't tell you what you're likely to observe, for obvious reasons.
It would be completely random, with all events being equally likely at every point in time. It would have no history, since the past has no effect on the present or future
You could plug a baby's nervous system into the output of a radium decay random number generator. It'd probably disagree (disregarding how crazy it would be) that its observations were best described by causal graphs.
I think it is a mistake to tie the question of what reality is to the particulars of the physics of our actual universe. These questions are about what it is to have an external reality, and the answers to them should be the same whether the question is asked by us in our current universe, or by some other hapless inhabitants of a universe bearing a distinct resemblance to Minecraft.
I can imagine types of existence which don't include cause and effect - geometrical patterns are an example - there are relationships, but they are not cause and effect relationships - they are purely spatial relations. I can imagine living in a universe where part of its structure was purely such spatial relationships, and not a matter of cause and effect.
Imagine a universe that is made only of ideal billiard balls eternally bouncing around on a frictionless, pocketless billiard table. Essentially the same thing as selylindi's idea of a gas in thermodynamic equilibrium. Imagine yourself observing this universe as a timeless observer, or to aid the imagination, that it's "time" dimension is correlated to our space dimension, so we see the system as an infinite frozen solid, 11 by 6 by infinity, with the balls represented by solid streaks inside that go in straight lines except where they bounce off each other or the boundary of the solid.
Now, this system internally has a timelike dimension, except without increasing or decreasing entropy. And the physics of the system are completely reversible, so we have no basis of saying which way is the "future" and which way is the "past" in this system. We can equally well say a collision at one time is "caused" by the positions of the balls one second in the "past" or one second in the "future". There is no basis for choosing a direction of causality between two events.
In our universe, our time is microscopically reversible but macroscopically irreversible, because of the fact that the universe is proceeding from a low entropy state (we call that direction the "past") to a high entropy state (the "future"). I am curious, can anyone coherently describe a universe with nothing similar to irreversible time, but with a useful notion of causation? Or with something like irreversible time, but no causation whatsoever? I have tried (for much more than five minutes!) and not succeeded , but I am still far from sure that it's impossible to do. It might be too much to ask to imagine actually being in a universe without causation or time, but perhaps we can think of how such a universe could look from the outside.
What is the difference between constraining experience and constraining expectations? Is there one?
At first thought. It seems that if it could be falsified, then it would fail the criteria of containing all and only those hypotheses which could in principle be falsified. Kind of like a meta-reference problem; if it does constrain experience, then there are hypotheses which are not interpretable as causal graphs that constrain experience (no matter how unlikely). This is so because the sentence says "all and only those hypothesis that can be interpreted as causal graphs are falsifiable", and for it to be falsified, means verifying that there is at least one hypothesis which cannot be interpreted as a causal graph which is falsifiable. Short answer, not if we got it right this time.
(term clarification) All and only hypotheses that constrain experience are falsifiable and verifiable, for there exists a portion of experience space which if observed falsifies them, and the rest verifies them (probabilistically).
I think that in a universe without a cause and effect structure, we'd tend to see more chaos than we do. Casual models would tend to fail to correspond to reality; all we could do is attempt to reason over joint probability distributions, which, as was explained, is kind of hopeless.
Well, my experiences could not be readily predicted by a simple Bayesian net. Thus I would expect the joint probability distribution on all things to be really complicated unless there were some other kind of pattern to it. Heck, maybe my experiences correspond to repeated independent samples from a giant multidimensional Gaussian or something (rotated of course so that the natural observable variables have non-trivial covariance).
Asserting that a particular causal model is an accurate description of the universe certainly constrains experience to fit the causal model. Asserting that it is possible to accurately describe the universe with a causal model is tautologically true because a fully connected model fits every possible probability distribution. Asserting that it is possible to accurately describe the universe with a simple causal structure constrains experience to match a simple causal model. If you know that the universe fundamentally works by running some causal model, asserting that the universe runs this particular causal model predicts that you will never find a more accurate causal model for describing the universe. I'm not sure how asserting that the universe fundamentally works by running some causal model would constrain experience.
I'm having a hard time making sense of the question. I'm sort of trying to imagine that there are no causal relations, and then opening my eyes to see what's different. Except 'seeing' and 'looking' don't make sense any more. What could it mean for something to 'appear'? I can't get a grip on even the idea of 'experience'.
At which point I conclude that either I am not imaginative enough, or the exercise is inconceivable.
If the universe were not governed by cause and effect, then we could not consistently improve our predictions of the future by observing the past, even by a little bit.
(Written before reading other comments.)
Assuming our universe is causal, then no you cannot. Any universe you can imagine has laws of physics which can be modelled by the interactions of the neurons in your brain, and are therefore causal.
There might be some things that can only be experienced in an acausal universe, but it is not possible for me to imagine them.
Physicists tell us that reality is, at the lower levels, described by differential equations. Those describing the temporal evolution of systems are generally hyperbolic differential equations. That is, they have microscopic causal structure: the properties at a point (x,t+dt) depend on the properties only in a small, finite neighbourhood of x at time t. This is what allows larger scale events to be described more abstractly in terms of causal graphs. (A known problem here is the time-symmetry of all these equations. I don't have a solution to that either.)
Some have speculated about the very finest scale being discrete, with fundamental laws of temporal evolution such as those of cellular automata or graph rewriting. That would also provide the fundamental causal structure from which causal structure on the macroscopic level emerges.
A universe whose fundamental laws were all elliptic differential equations -- those in which a change in boundary conditions in one place changes the solution everywhere at once -- would not support causal reasoning. Everything depends on everything else and none of its emergent phenomena would be describable by sparse causal graphs. I'm not sure you could have agents within such a universe, for it to look like anything to them, or any notion of time, but we can imagine such universes from outside.
In a universe without causal structure, I would expect an intelligent agent that uses an internal causal model of the universe to never work.
Of course you can't really have an intelligent agent with an internal causal model in a universe with no causal structure, so this might seem like a vacuous claim. But it still has the consequence that
P(intelligence is possible|causal universe)>P(intelligence|acausal universe).
That seems plausible but I must admit that I don't know enough details about possible "acausal universes" to be particularly confident.
If intelligence is seen as optimization power- in the sense of agents that constrain possible futures for their benefit- then it seems clear that the rewards to intelligence are 0 or negative in acausal universes, and so they should be less likely than in universes where they have positive rewards.
This one is great - it really does have the contradictory nature of traditional koans.
Just try to picture what you would do to test whether the universe was causal, and how we would adjust our models based on such a test.
I suppose I would say that reality would look as if things happened with no observable pattern related to the things that happen before them, but looking at things requires a long causal chain between photons being emitted and signals in my brain. Supposing I happened to somehow flash into existence for an instant in a noncausal world, or that causality suddenly failed, I would not expect to be able to experience anything past that point since my experiences depend on so many causal processes.
An acausal world would be a world where there is experience (some kind of 'reality') but without the possibility of contradiction. It is like a dream, where what you experience is a story and that story can be written over, and can shift, at any moment, without contradiction. So at one moment you see a cup, and then the next moment, you didn't see a cup. It's not that the cup changed or that you were mistaken, it's just that at first your experience was "seeing a cup" and then at the next moment your experience was, "I wasn't there to see that cup". The experiences both happened: You saw it. And you weren't there and didn't see it. It's a string of happenings connected by the word 'and' : I saw a cup and I didn't see a cup and I was there and I wasn't hungry and the grape hurt.
This isn't an original idea, I realize now. I've read of a place like this in at least a couple science fiction stories.
A causally disconnected event would not affect our experience, so no, it does not constrain our experience. But it wasn't meant to: it was meant to constrain our maps, not our experience. To stop us from believing meaningless statements.
Every causally separated group of events would essentially be its own reality.
Several possible examples come to mind for a universe with no cause or effect.
First is a universe with only one thing in it, so that there's nothing for it to be causally connected to.
Second is a universe with multiple things in it that could in principle interact but due to the set-up of the universe never actually do interact. For example, a universe of rigid particles in a void where they would interact if they struck, but the distances between all particles are too great for that to occur in the lifetime of the particles.
Third, a universe in which its entities do interact, but nothing ever changes, so there are no nontrivial correlations. Perhaps count a universe of mutually repelling particles in a void, arranged in an unchanging crystalline structure.
Fourth, more loosely, is a universe in which its entities do interact and change, but the arrangement of all the things is such that only minimal correlations arise. Perhaps a universe analogous to a closed system containing a gas at thermodynamic equilibrium.
Prescinding from those, the idea that everything in our universe is made of causes and effects constrains my expectations in that there should multiple things (check) that actually interact (check) and change (check) and have nontrivial correlations (check). Other than the continuation of such things, I can't readily think of any sense in which the idea constrains my expectations for future experiences.
To clarify you are pointing out that without cause and effect, stars would not even form, or even baryons for that matter. A gas at thermodynamic equilibrium probably would not be conscious, so from there we can go straight for the Anthropic Principle. Otherwise the question has no real solution--like asking what a peacock would look like if eyes didn't exist. (Handoflixue already killed this horse, though--sorry for beating it.)
Any time a theory of cosmology implies that you're a Boltzmann brain, run. ;)
To answer this, I need to answer another question: What would the universe look like if it did not have the structure of causal models? If I know that then I can know whether or not that universe looks different than ours.
So we're talking about a universe where there is no A --> B causal connections. Where you can't accurately say something like "When I eat, it causes me to be less hungry," or even say anything, since "saying" something requires some sort of causal ability: the ability to push air in intensional patterns.
And that universe... really doesn't look like ours. I might want to talk about a universe where there are correlations but not causations, but then how do I explain the correlations? Are they just brute facts? That seems unlikely. But even in that event, I would expect rules to break down in chaotic ways: one day, food wouldn't make me feel nourished. And it wouldn't be because I ate the wrong foods or something like that, it'd just be because the correlation broke down. And that really doesn't look like our universe either. I may be wet because it was raining, but I don't get wet merely because some 'correlation' between 'sunnyday" and "notwet" broke down.
Actually we aren't. We are talking about an universe where there are effects that happen without cause. That doesn't mean that effects that have causes aren't allowed.
Hm. That is conceptually possible, I suppose. Although I can't really imagine how that sort of demarcation criteria would work.
I would expect not exist in a way that suggests causality, e.i. being born and then expecting death, rather than the other way around. This is hard for me to imagine because I didn't really evolve for that world. It's possible that our universe doesn't work that way at the smallest level, but it seems might suspicious that random events lead to a largest world that operates very deterministically. Still, it is possible that this is just the manifestation of probabilistic laws at the smallest level. It's definitely paying rent so far,(for those who do the experiments) so that's we're going with, and there hasn't been a good argument or experiment against it yet.
Infintesmal "violations" of causal laws as manifestations of probabilistic laws don't seem to effect me very much. Large ones that would pay rent haven't happened on the level that would pay rent on an evolutionary or personal level, and, as I understand it (which is not terribly well) these probably won't happen unless the universe ran from the big bang to heat death a couple hundred times.
I can make models in my head where the universe (on my scale) is really chaotic, but looks deterministic because of a conspiracy by matrix gods or whatever, but that seems to violate Occam's Razor, for what that's worth when matrix gods control your life.
No. For any set of observations O1, O2, ..., O_N, you can construct an overprecise causal model that links some central cause to nodes O1, O2, ..., O_N. [That is, our causal model is: "You observed O1 because God willed it. Then you observed O2 because God willed it..."] Thus causal models can explain any set of observations. Constraining experience requires in addition some sort of Occam's Razor that prefers simpler causal models.
I'd agree with the assertion "Unknowable relationships are equivalent to no relationship". In other words, cause-and-effect is only meaningful if we have some ability to gather information as to the nature of the relationships. Occam's Razor is one such method, but I wouldn't assume that it's specifically required - we could just as easily be born with divine insight as to the cause-effect relationships.
Yes, to a limited extent I think I can.
A universe without a completely causal structure would have to have a number of effects that have no cause. (This need not apply to all effects in this universe, merely to a subset of effects). The Steady-state universe, a now abandoned alternative to the Big-bang model, may be an example; in the steady-state universe, if I remember correctly, it was theorised that small bits of matter (hydrogen molecules) appeared out of nowhere at random times, at a very low rate. This is an example of an effect without a cause.
Alternatively; consider a universe where a man suddenly appears out of nowhere in the middle of a public area. He claims to be a time traveller, from fifty years in the future, coming back in time to prevent some terrible disaster. Though his story is unbelievable, the disaster he predicts is prevented. Fifty years pass, and the time traveller is not sent back to the past (since the disaster was, after all, prevented). This does not cause a paradox (the laws of this universe are that matter can appear at any time, in any arrangement, including a person with false memories of time time travel from a non-existant future) Such a potential universe thus has an effect (the man appears) without a cause.
The examples don't quite work. In that steady-state universe, the appearing matter subsequently interacts and so is causally connected to the rest of the universe. You just have to trace the connections backwards, and eventually you reach a stopping point. Similarly with the false time traveler: he causally affected the world, so he's clearly part of a chain of causes and effects.
It's a separate question to ask whether everything has a causal in-connection and a causal out-connection. Both your examples, and epiphenomal theories of mind, are meaningfully about unidirectional causal links.
Hmmm. I had been trying to consider the case where some events have no causes. Now, you're pointing out - as I understand your argument, and please correct me if I am wrong - that the same event can be a cause, and therefore that it is a part of an interconnected causal universe.
This is an interesting argument. If I notice the existance of something, then that is a causal relationship; it exists, and this causes me to notice it by some means. Therefore, anything that I observe shares a causal relationship with the fact of its observation; if that is enough to consider it part of a causal universe, then I can only observe a causal universe. I cannot imagine anything that I cannot, by definition, observe in any manner (including by any deduction) constraining my experience.
On the other hand, I can (at least in certain imagined universes) observe effects without causes; I can observe the time traveller appearing for absolutely no reason.
I had assumed the question was "a universe where an event can have out-connection but not in-connection" (and the consciousness one was about having an in-connection but no out-connection).
In a universe with NO connections, you wouldn't get patterns, much less emergent patterns - no atoms, no stars, no planets, no life, not even internet!
Multiple segregated causal networks would be multiple realities (I think the simplest reference would be to think about two different books or virtual worlds, although there's actually still some connection there)
Individual events which have out-connections but not in-connections, by contrast, seems like a fairly interesting question to explore. Why DO we assume that all evens have in-connections? Why not just assume the weather is because Zeus is mad, and Zeus' emotions are beyond the ken of mortal minds?
Not all, the past doesn't have in-connections and the future doesn't have out-connections.
Can you explain what you mean by that? I tend to model past events as having even-further-past causes. I definitely model future events as having even-farther-future ramifications. So they'd seem to generally have both in and out.
I was referring to the past (or future) as a whole.
No. I literally assign prior probability zero to the statement that the universe is not made out of causes and effects, because there is causal structure in Turing machines and in all Turing-complete models of computation which could make up the Solomonoff prior. Causal structure is a very broad thing - it's just a sparse graph of interacting entities with a lattice ordering.
I can imagine a universe in which the local ordering I observe doesn't go as far forward or back as I thought, and the true everything-is-causes-and-effects structure is pushed one layer back to something completely hidden from me. I can imagine a universe in which I've falsely inferred an ordering which isn't there, and getting confused by cycles in a graph that I thought was causal. But a universe with no causality at the lowest layer - I think causality is inherent in too many things, and that after subtracting those things there's not enough option space left to make a universe out of.
If you can't imagine an universe that's not made out of causes and effects than talking about such an universe is meaningless.
To be able to assign a probability zero to the statement that the universe is not made out of causes and effects you have to be able to imagine a universe that's not made out of causes and effects.
Meaningless statements can't be true or false. Speaking about their probability makes no sense.
Before Einstein nobody could imagine without universal time either.
In other words, if you can't imagine a universe with property X, that's a fact about you not about the universe.
In other words, causality is the invisible pink unicorn.
I don't understand this reply at all, except as an indication that I didn't communicate these concepts as well as I'd hoped.
The text I quoted in the grandparent seems to be saying that even if the universe doesn't contain causality, we can always postulate an external causality structure even if most of it can't be observed.
I think this is one of the few instances where p(0) is actually appropriate! :)
How about mild violations of causality?
That isn't a violation of causality, it's just a universe with time that goes infinitely far forward and back.
Time appears to stretch backward infinitely, because local causality still looks nice. But actually it only stretches backward to now. If time was actually a straight line rather than a cycle, then one could intervene in this system and it would only change the future. But if you intervened in a cyclic system, you would find that you had changed what looks like the past.
In fact, self-consistency constraints would kick in and logically prevent you from some sorts of intervention that would make perfect sense if time stretched off to infinity - it's like using quantum mechanics instead of classical mechanics, where classically it seems like you should be able to have any amount of energy you want.
More philosophically, we've run into Aristotle's distinction between self-cause and infinite regress. And also why Bayesian networks are typically defined as directed acyclic graphs, thus putting cyclic graphs outside of the hypothesis-space.
I think I understand your distinction between infinite regress and cyclical causation, but I don't understand why that implies a cyclical universe violates causality. To rephrase jimrandomh: that isn't a violation of causality, it's just a universe with cyclical time.
Well, one can still think of it causally - you can still draw a graph with arrows, at least. But it's atypical causality.
Typical causality is like kicking a ball. The ball sits still until you kick it, and you can kick it however you like and it will roll away. But once you have loops, it's like if the ball had to go through a portal to the past and kick itself. As soon as you try to kick the ball, the ball you would have kicked has already gone back to the past and hit itself in a way consistent with the motion of your foot, so it will feel quite unlike kicking the first ball. And in fact it is physically impossible to move your foot in a way inconsistent with the ball being the cause of its own motion, even though trying to kick the ball restricts the possibilities - or rather, being able to try to kick the ball tells you that the possibilities were already restricted...
In typical causality, the ball has a reason for moving the way it does - you can trace the motion backwards to some acceptable starting point, like "I kicked it as hard as I could toward the fence." When you add cycles, tracing the chain of arrows back does not need to end at anything you find remotely satisfactory or even unique - "the ball moved because it hit itself because it moved because it hit itself..."
This is a problem with your personal intuitions as a medium-sized multicellular century-lived mammalian tetrapod. No event in this chain is left uncaused, and there are no causes which lack effects in this model. Causality is satisfied. If you are not, that's your problem. Hell, the energy is even conserved. It runs in a spatial as well as a temporal circle, what with the ball hitting itself and skidding to a stop exactly where it was sitting to wait for the next hit. On the other hand, in such a universe quantum mechanics does not apply, because worldlines cannot split, which also removes any possibility of entropy. ALL interactions are 100% efficient.
My first answer is that the idea of 'interventions' comes from causality- if I don't like being wet, and it's raining, I can deploy an umbrella, and that will make me not get wet(ter) from the rain. The idea that everything is made of causes and effects meaningfully constrains actions, because an agent that understands causes can manipulate reality better than an agent which doesn't understand causes.
But that's just a further elaboration of what reality looks like now. It's difficult for me to imagine a world without causality- and I don't think that's just because I (like most humans) am a deeply causal thinker. Causal models are just math, and so they can be imagined just like multiple spatial geometries can be imagined, regardless of what the universe's real shape is. I think you would need to have a universe in which no causal models could be justified by the data, which would be an incredibly strange place.
And, actually, by the definition of universe you use in the post, a universe without a causal structure would just be a single node, forever alone.
Koan 2:
"Does your rule there forbid epiphenomenalist theories of consciousness - that consciousness is caused by neurons, but doesn't affect those neurons in turn? The classic argument for epiphenomenal consciousness has always been that we can imagine a universe in which all the atoms are in the same place and people behave exactly the same way, but there's nobody home - no awareness, no consciousness, inside the brain. The usual effect of the brain generating consciousness is missing, but consciousness doesn't cause anything else in turn - it's just a passive awareness - and so from the outside the universe looks the same. Now, I'm not so much interested in whether you think epiphenomenal theories of consciousness are true or false - rather, I want to know if you think they're impossible or meaningless a priori based on your rules."
How would you reply?
"We can imagine any number of universes, that does not always lead to a good argument. In this case, the main issue with the argument is that while we can imagine that universe, it doesn't look like ours. There's no talk of consciousness, there's no self-reflection. Those are things in reality clearly caused by a link between our thoughts and our brains, one that goes in both directions.
Imagining a world in which people act exactly like people do now, but without a consciousness, strays so clearly outside the bounds of Occam's Razor that there doesn't seem to be any point in thinking about it. Adding in a mysterious 'zombie master' to make the zombies act as though they had consciousness... Well at this point, we're not talking about anything remotely resembling reality. This entire thought experiment in no way gives us any truths about reality whatsoever. It is completely meaningless."
[Cheating, since I already read some Zombie sequences, but have not read any replies in this thread] The consciousness causes you to speak of consciousness, which is the result of neurons in your brain firing your jaw muscles (and other muscles, and so on). If it was epiphenomenal enough that none would talk about it, we wouldn't have this question in the first place.
[Has consciousness] --> [Writes books/blogs on consciousness]
Causually connects consciousness to the universe.
If consciousness is epiphenomenal, then what generated your question? I assume you are positing non-conscious people who ask all the same questions about consciousness that we do.
I don't see a reason to rule out neuron-generated epiphenomena a priori - for example, the most elegant explanation of the phenomena might predict some entity that cannot be measured directly, and never affects anything measurable after its generation - but if they existed, we wouldn't notice and wouldn't ask questions about them. Therefore, whatever real thing it is you're asking about cannot be an epiphenomenon.
If true consciousness is an epiphenomenon, then your question is not motivated by experiencing true consciousness. If your question is motivated by experiencing true consciousness, then true consciousness is not an epiphenomenon.
I like your koan responses. They seem like the sort of thinking and arguments that could actually be useful in a discussion, too.
Thanks.
It started as a tiny set-piece speech about how consciousness couldn't be an epiphenomenon, which is explicitly what the koan isn't asking about. I had to rewrite several times before it seemed like the sort of thing that might actually engage the questioner.
I'm still not sure I actually answered the koan, though...
I think your answer is very much what the koan was meant to generate. Simply saying 'No, I don't a priori eliminate epiphenomenal theories' seems like it'd miss the point entirely. You tackle the source of the concern or question, and conclude with a very good "If A, B, if ¬A, C" statement that easily follows from your arguments.
More importantly, your answer seems to completely reduce the problem and dissolve the question.
It does not. Epiphenomenal consciousness could be real for the same reason that the spaceship vanishing over the event horizon. It's Occam's Razor that knocks down that one.
A strict reading of the rule suggests that it doesn't; consciousness is caused by neurons, and we observe neurons.
As with the psychic cousin, this particular rule doesn't seem to forbid it outright (at least not in the obvious way). But a node thrown in with only one link to the rest of the universe still seems suspicious. It smells of an ad hoc hypothesis even before we ask if it means "consciousness" in the usual sense.
(For this one I only saw Emile's comment.)
With the above solution, then yes epiphenomenalist theories of consciousness are meaningful. They clearly describe networks in which consciousness connected to the rest of reality that you experience. On the other hand, I think that this is because the above statement fails at its intended goal rather than that these theories are actually meaningful. In particular I think one should append to the above:
"Furthermore, it must not be possible to remove this stuff (and perhaps some other stuff) from your causal network without affecting things that you can experience."
For any precise definition of consciousness that fits epiphenomenalism, it would be meaningful. However, to my knowledge, no such precise definition has been put forward.
It doesn't rule it out. Unless you're directly observing those epiphenominal nodes, Occam's razor heavily decreases the likelihood of such models though, because they make the same predictions with more nodes.
So if Universe A features epiphenomenal consciousness, and Universe B doesn't, and that we consider the statement that we are in universe A and not universe B, then looking back at the rule:
These "causal links" you trace out are part of the map, not part of the territory - you have to be able to deduce their existence. And in this case (unlike the spaceship scenario), there is no way anybody can deduce the existence of the neuron -> consciousness link, since by definition nothing can be observed about the consciousness.
=> so, firmly in the "meaningless" camp.
(Written without reading other comments.)
The theory does not forbid a node from having no causal effect on anything else, which is what I think an epiphenomenal consciousness would be. But such a node could not be measured. A logical positivist would say this makes the theory meaningless, and I'm inclined to agree.
Conceivably, if the universe runs on a computer, there could be a node which cannot be measured from inside the universe but could be measured from outside. Perhaps debug info is turned on, and any time neurons fire in patterns that match some regex, the word "consciousness" is printed to stderr. I would not say this is meaningless; if it is true, it gives us a way of communicating with whoever is watching stderr (but no guarantee that such a being exists or would talk back).
But it is not suitable as a theory of consciousness, unless you want to stipulate that neurons write about consciousness for reasons that are completely uncorrelated to consciousness.
You can account for a theory where neurons cause consciousness, and where consciousness has no further effects, by drawing a causal graph like
(universe)->(consciousness)
where each bracketed bit is short-hand for a possibly large number of nodes, and likewise the -> is short for a possibly large number of arrows, and then you can certainly trace forward along causal links from "you" to "consciousness", so it's meaningful. And indeed for the same reason that "the ship doesn't disappear when it crosses the horizon" is meaningful.
We reject epiphenomenal theories of consiousness because the causal model without the (consciousness) subgraph is more simpler than the one with it, and we have no evidence for the latter to overcome this prior improbability. This is of course the exact same reason why we accept that the ship still exists after it crosses the horizon.
Draw a Venn Diagram, with "things that are causes" and "things that are effects" (get-caused-by-other things). The intersection in the middle is "reality"
Consciousness, in this model, is "effect, but not cause" - it doesn't change any of our anticipations about the rest of the universe, and is therefor meaningless (but not intrinsically impossible)
Psionics, in this model, is being asserted as "cause, without effect" - either it actually is effected by the state of reality, and thus correlates with reality (in which case it is part of "reality"), or else it is not correlated to reality and thus cannot produce useful information on the state of said reality.