Related to: Dissolving the Question, Words as Hidden Inferences

In what sense is the world “real”?  What are we asking, when we ask that question?

I don’t know.  But G. Polya recommends that when facing a difficult problem, one look for similar but easier problems that one can solve as warm-ups.  I would like to do one of those warm-ups today; I would like to ask what disguised empirical question scientists were asking were asking in 1860, when they debated (fiercely!) whether atoms were real.[1]

Let’s start by looking at the data that swayed these, and similar, scientists.

Atomic theory:  By 1860, it was clear that atomic theory was a useful pedagogical device.  Atomic theory helped chemists describe several regularities:

  • The law of definite proportions (chemicals combining to form a given compound always combine in a fixed ratio)
  • The law of multiple proportions (the ratios in which chemicals combine when forming distinct compounds, such as carbon dioxide and carbon monoxide, form simple integer ratios; this holds for many different compounds, including complicated organic compounds).
  • If fixed volumes of distinct gases are isolated, at a fixed temperature and pressure, their masses form these same ratios.

Despite this usefulness, there was considerable debate as to whether atoms were “real” or were merely a useful pedagogical device.  Some argued that substances might simply prefer to combine in certain ratios and that such empirical regularities were all there was to atomic theory; it was needless to additionally suppose that matter came in small unbreakable units.

Today we have an integrated picture of physics and chemistry, in which atoms have a particular known size, are made of known sets of subatomic particles, and generally fit into a total picture in which the amount of data far exceeds the number of postulated details atoms include.  And today, nobody suggests that atoms are not "real", and are "merely useful predictive devices".

Copernican astronomy:  By the mid sixteen century, it was clear to the astronomers at the University of Wittenburg that Copernicus’s model was useful.  It was easier to use, and more theoretically elegant, than Ptolemaic epicycles.  However, they did not take Copernicus’s theory to be “true”, and most of them ignored the claim that the Earth orbits the Sun.

Later, after Galileo and Kepler, Copernicus’s claims about the real constituents of the solar system were taken more seriously. This new debate invoked a wider set of issues, besides the motions of the planets across the sky. Scholars now argued about Copernicus’s compatibility with the Bible; about whether our daily experiences on Earth would be different if the Earth were in motion (a la Galileo); and about whether Copernicus’s view was more compatible with a set of physically real causes for planetary motion (a la Kepler).  It was this wider set of considerations that eventually convinced scholars to believe in a heliocentric universe. [2]

Relativistic time-dilation: For Lorentz, “local time” was a mere predictive convenience -- a device for simplifying calculations.  Einstein later argued that this local time was “real”; he did this by proposing a coherent, symmetrical total picture that included local time.

Luminiferous aether:  Luminiferous ("light-bearing") aether provides an example of the reverse transition.  In the 1800s, many scientists, e.g. Augustin-Jean Fresnel, thought aether was probably a real part of the physical world.  They thought this because they had strong evidence that light was a wave, including as the interference of light in two-slit experiments, and all known waves were waves in something.[2.5]

But the predictions of aether theory proved non-robust.  Aether not only correctly predicted that light would act as waves, but also incorrectly predicted that the Earth's motion with respect to aether should affect the perceived speed of light.  That is: luminiferous aether yielded accurate predictions only in narrow contexts, and it turned out not to be "real".

Generalizing from these examples

All theories come with “reading conventions” that tell us what kinds of predictions can and cannot be made from the theory.  For example, our reading conventions for maps tell us that a given map of North America can be used to predict distances between New York and Toronto, but that it should not be used to predict that Canada is uniformly pink.[3]  

If the “reading conventions” for a particular theory allow for only narrow predictive use, we call that theory a “useful predictive device” but are hesitant about concluding that its contents are “real”.  Such was the state of Ptolemaic epicycles (which was used to predict the planets' locations within the sky, but not to predict, say, their brightness, or their nearness to Earth); of Copernican astronomy before Galileo (which could be used to predict planetary motions, but didn't explain why humans standing on Earth did not feel as though they were spinning), of early atomic theory, and so on.  When we learn to integrate a given theory-component into a robust predictive total, we conclude the theory-component is "real".

It seems that one disguised empirical question scientists are asking, when they ask “Is X real, or just a handy predictive device?” is the question: “will I still get accurate predictions, when I use X in a less circumscribed or compartmentalized manner?” (E.g., “will I get accurate predictions, when I use atoms to predict quantized charge on tiny oil drops, instead of using atoms only to predict the ratios in which macroscopic quantities combine?".[4][5]


[1] Of course, I’m not sure that it’s a warm-up; since I am still confused about the larger problem, I don't know which paths will help. But that’s how it is with warm-ups; you find all the related-looking easier problems you can find, and hope for the best.

[2]  I’m stealing this from Robert Westman’s book “The Melanchthon Circle, Rheticus, and the Wittenberg Interpretation of the Copernican Theory”.  But you can check the facts more easily in the Stanford Encyclopedia of Philosophy.

[2.5] Manfred asks that I note that Lorentz's local time made sense to Lorentz partly because he believed an aether that could be used to define absolute time.  I unfortunately haven't read or don't recall the primary texts well enough to add good interpretation here (although I read many of the primary texts in a history of science course once), but Wikipedia has some good info on the subject.

[3] This is a standard example, taken from Philip Kitcher.

[4]  This conclusion is not original, but I can't remember who I stole it from.  It may have been Steve Rayhawk.

[5] Thus, to extend this conjecturally toward our original question: when someone asks "Is the physical world 'real'?" they may, in part, be asking whether their predictive models of the physical world will give accurate predictions in a very robust manner, or whether they are merely local approximations.  The latter would hold if e.g. the person: is a brain in a vat; is dreaming; or is being simulated and can potentially be affected by entities outside the simulation.

And in all these cases, we might say their world is "not real".

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The idea of leaky abstractions seems relevant here. This is the observation from engineering that when layers of models are built on top of each other, consequences of the lower-level models tend to appear even when the higher layers are meant to abstract them away.

Asking whether a model is "real" seems akin to asking whether its abstraction will ever leak, and if it does, whether the places where lower layers show through are correctly labelled and explained within the model. Atomic chemistry is "real" in that, when it does break down (extreme energies, rare particles, etc), it's for reasons that can be explained in atomic chemistry's own vocabulary. On the other hand, psychology, for example, tends to break down for reasons that can't be explained, or can only be explained in terms of biology.

Under this definition, if the universe is a simulation, then it is real if and only if that simulation runs to completion without information about the simulator's universe leaking into our universe.

Atomic chemistry is "real" in that, when it does break down (extreme energies, rare particles, etc), it's for reasons that can be explained in atomic chemistry's own vocabulary. On the other hand, psychology, for example, tends to break down for reasons that can't be explained, or can only be explained in terms of biology.

I'm not sure I follow this. Isn't atomic chemistry an abstraction describing the behavior of the wave function? How are the places it breaks down explained by it's own vocabulary?

It's an interesting question, and probably the right way to ask it, but I've noticed three errors or omissions that would make me very happy if they were fixed. I'll start with the minor nitpicks.

  • Lorenz thought his transformed time wasn't real because he was preserving the aether, which defined a particularly "real" time. Before Einstein's interpretation of the photoelectric effect the aether made a lot of sense, which seems like useful context.

  • Hydrogen monoxide isn't something early chemists would have measured - maybe they measured hydrogen peroxide, though. Other examples for the law of multiple proportions would be carbon dioxide and carbon monoxide.

  • The Copernican model was not more accurate than the Ptolemaic model. Its inaccuracy was its major problem, in fact. The main reason it held on was that it, in its simplicity, felt more "real" - what you report was only thought later. Kepler's model, on the other hand, kicked butt and took names, which may be what you were thinking of.

Much thanks for the good historical info. I'm confused still. This one sounds consistent with what I said; a local time was useful in prediction but didn’t provide enough predictions in varied enough contexts for it to seem more sensible to believe in local time as a real world-constituent, rather than as a narrowly useful predictive device. Are you saying this wouldn’t have been true without the aether as a specific such context? Thanks. Fixed. Okay, thanks. I’ll fix that. Do you think historians of science are correct in thinking that the scholars at Wittenburg in fact engaged with the new theory, but not with the bit about heliocentricness?
Re: Lorentz, I think this discussion might prove helpful, especially the very astute comment #9 there:

Very small children understand "real" to be "what's inside" -- what's hidden, essential. Sometimes literally inside: ask toddlers "If you took a dog, and gave it the bones and insides of a cat, would it still be a dog?" they say "no," but "If you took a dog and made it look like a cat on the outside, would it still be a dog?" they say "yes." (I'm getting this from Paul Bloom's "How Pleasure Works.") Young children are essentialist about gender as well -- they assume more differences between the sexes than actually exist, not fewer.

What psychological evidence I've seen suggests that we're in some way wired to see categories as real. "Natural kinds." To think that there's a real difference "out there" between dog and not-dog, not just a useful bookkeeping convention. I'm inclined to believe that Anna's reasoning about "atoms are real" and Eliezer's reasoning about categories actually make more sense than essentialism -- but I suspect that this kind of question-dissolving is not the standard, evolution-provided brain pathway.

If the subject interests you, I recommend reading Women, Fire, and Dangerous Things. It's somewhat slow going, but the author lays out a detailed story about the process of category formation in humans (that is, why we create the categories that we do) that does wonders for clarifying the issues involved. I have no idea whether the specific story he tells is right or not, but sometimes it's useful to just have an example of what such a story might look like.
1Дмитрий Зеленский1y
EXTREMELY late to the party, but I have to warn a potential lurker against Lakoff's book as a linguist. His stories are extremely just-so-stories - or even just-not-so-stories.
Real-world example: The creationist science of baraminology takes assumption of kinds to its logical limits. Todd Charles Wood comes so close to admitting his baraminology work is excellent evidence for evolution. It's amazing how far people will take an obviously broken axiom without letting go of it.

Interesting. It's funny how the Bible really reinforces the idea of natural kinds -- a lot of the prohibitions can be interpreted, one way or another, as prohibitions against mixing things that are essentially different (wool and flax, men and women, fish and mammals.) It would make sense if essentialism was the way we "naturally" think, and it takes some scientific development to tease out where it doesn't make sense.

Though I'm just amazed at their trouble with grammar, first of all. Grrrr.

* wool and flax - Yes * men and women - Huh? * fish and mammals - Sort of (some people do not eat milk and fish with same utensils, but it's not from the Bible as far as I can tell) Additionally - * mixing plant species (via grafting) - Yes, a major support for your point -- your local ex-rabbinical student :)
-men and women: men aren't supposed to dress like women and vice versa. -fish and mammals: takes some unpacking and was probably the wrong way to phrase it. The fish you can eat should have scales and fins -- that sort of points to "good" fish being especially "fishy" fish. Fish that are kind of not like fish are not okay.
agreed, support your theory yes, probably wrong way to phrase it, but I agree about the essentialism of "fish with scales" being "fishy fish" - that's a very sharp observation, actually.
I herded the RW article from silver to gold (in the front cover rotation) and it was quite difficult. It's one of those subjects where every single thing about it is blitheringly stupid, and putting the stupidities in an order that reads usefully as an essay is actually the hard part. The inferential distance problem here is getting across to people that other people really do believe things this stupid. Staying understated requires remarkable self-control. Project Blue Beam was another - saving the punchline for the end, where it doesn't belong logically but does belong narratively.
Heh. What are cooties anyway?
Another know how cross-cultural belief in cooties or the equivalent is?
Originally, they were lice.
What would it be, to not see categories as real? All of our perceptions, from low-level physical sensation up to the highest abstractions, are experienced as real things existing outside of ourselves. This is an illusion in every case. Look around you and it will seem to you that you see objects "out there". Listen, and you seem to hear things far off. Touch something and the sensation appears to be at your skin. Smells seem to be in the air around you, and tastes seem to belong to what you are eating. Watch someone in action and it will seem as if you can see their purposes, right out there in the other person. Think about abstractions like "justice" or "democracy", and these too will seem to be externally existing things. But all of that experience is literally in your head. We are all of us shut up inside three pounds of porridge in a bone box, but it never feels like that. There is something outside you that gives rise to these sensations, but it takes a lot of work to get anywhere close to the real story. We are wired to perceive categories -- and sensations, and sequences, and patterns, and various other sorts of perception. The perceptual illusion affects all of them.
I expect it would be noticing that I treat X as though it were importantly similar to Y, even though X is (it seems to me) nothing at all like Y. This happened to me a lot while I was dealing with post-stroke PTSD... I would react to things in ways that made no sense to me at all, think about it for a while, and eventually conclude that I was treating those things as importantly equivalent to aspects of stroke-related trauma, even though they didn't seem to me to be importantly equivalent at all. Our minds are not internally consistent. Agreed about the rest of this, though. "Aaaa! I'm stuck inside this dark, damp skull!" just isn't the sort of thing brains are wired to experience.
Hawkins would agree.

This might be a situation where a word ("real") that served some useful purpose in certain contexts has been unwittingly taken out of that context, resulting in a meaningless question that can be dissolved by understanding the original context.

This seems to be the method that Wittgenstein uses to dissolve questions in Philosophical Investigations.

Half the more "philosophical" posts on here seem like they're trying to reinvent the wheel. This issue has been discussed a lot by philosophers and there's already an extensive literature on it. Check out for starters. Nothing wrong with talking about things that have already talked about, of course, but it would probably be good at least to acknowledge that this is a well-established area of thought, with a known name, with a lot of sophisticated thinking already underway, rather than having the mindset that Less Wrong is single-handedly inventing Western philosophy from scratch.

Alternately, Western 'word salad' Philosophy might benefit from a bit of reinventing:

This is essentially the debate between scientific realists and anti-realists in philosophy of science. Realists hold that unobservable entities postulated by scientific theories are still "real"; anti-realists hold that these entities are not real. One of the big problems for anti-realists, as you pointed out with your first example, is that "what is observable" changes over time (e.g. we can now "see" atoms in ways that would have startled physicists in the 1860's). However, the anti-realists do have one interesting argument ... (read more)

The point I am trying to make is this: your question is one of those "great unsolved problems in philosophy."

The usual "great unsolved question of philosophy' is "Are atoms real?". I'm not trying to ask that question. I'm instead asking what disguised empirical inquiry scientists were engaged in, when, in the course of ordinary scientific research (and not metaphysical debates) they tried to figure out whether atoms were real.

Contemporary philosophers call this conceptual analysis and it's exactly how they talk about scientific realism and anti-realism. Your answer to the question, that X is real if it can be included as part of a coherent whole with the rest of science is vaguely Quinean.
I agree with the resemblance to Quine; it could also be thought of as Philip Kitcher's "unification" model of explanation.
And also the coherence theory of truth (replace "X is real" with " 'X exists' is true").
Are there great solved problems in philosophy?

People have solved good chunks of "Why do all dogs resemble one another", which is a problem that Plato cared a lot about. (Mendelian genetics, Darwinian evolution, and our understanding of how the brain clusters perceptions are all parts of the answer here.)

People have also solved good chunks of: "Is there a God?", "Is there likely to be an after life?", and "In what sense do we have free will?", among other questions.

People have also solved good chunks of: "Is there a God?", "Is there likely to be an after life?", and "In what sense do we have free will?", among others.

If a problem is solved in philosophy, but nobody reads it ...

Of course, if all we care about are lay beliefs the same could be said for physics, biology and neuroscience.

Good point. But I think it is the case that almost everyone who has need of (i.e. uses) information from physics, biology, and neuroscience uses the standard, though esoteric, information produced by scientists. But people who need (i.e. make decisions based on) ideas from philosophy regarding metaphysics, generally do not make use of what you and I might call the "state of the art" in this field.
Sure, unfortunately acting on the false beliefs that there is a God and you have a soul doesn't leave the loud and fiery explosions that acting on false beliefs about physics does.
Unless you count religious warfare, that is.
Why not just the last of those? All dogs resemble one another because if they didn't have a critical resemblance, we wouldn't use the same label for them. Even today, we often have common-use terms for organisms, where the labels (taken literally) violate post-Darwinian understanding, and that's because of what the layperson considers a relevant similarity. In other cases (e.g. "is a whale a fish?"), a deeper awareness of the relevant similarities did cause us to change up our label.
That would only be a sufficient answer to the question "Why do we have a category called 'dogs' such that all of its members resemble one another?". Genetics, evolution, etc. are indeed necessary to answer the question about the referent rather than the quotation.
Only because he picked a specific category where the (apparently-significant) physical resemblance did in fact coincide with a genetic resemblance. But because he picked a class of animals ("dogs") due to other criteria, the answer to that question begins and ends with his classification algorithm and what his mind counts as "doglike". It's quite common (as I made clear) for people to give the same name to genetically distant organisms or organs. The reason for physical similarity in that case is quite different from the reason in the case of the genetically similar organisms. To base your answer to Plato on dogs' genetic similarity, you would also have to "explain" sharks and dolphins as being the same species -- the "species" of fish.
Here, too, one search out scientific explanations for how the similarities arose -- this time having to do partly with how form is passed along within a species (genetics), and partly with convergent evolutionary pressures that lead sharks and dolphins to both have a streamlined shape, flippers, etc.
Yes, I get that. But, again, Plato didn't create a category isomorphic to modern knowledge of genetic lines. He created a category based on what Greeks at the time deemed "doglike". And the answer to that question is purely one of "why do you consider a boundary that includes only those things you call 'dogs' worthy of its own label?" Only later, as humans gained more knowledge, could they ask more complex questions about organisms that require knowledge of genetics, selection pressures, and convergent evolution. But the Greeks were not then at that point. Also, explanations having to do with how humans deem something doglike are scientific. Edit: To make the point clearer, consider ansewring Plato by saying "dogs are similar because genes determine what an animal looks like, animals reproduce by passing genes, and all dogs have similar genes". Such an answer would be wrong (uninformative) because it uses the premise "animals you give the same label to are similar because they have genes proportionally similar". This model is wrong, as it requires (per my above comment) you to also tell Plato that "shark-fish and dolphin-fish are similar because genes determine what an animal looks like, animals reproduce by passing genes, and all fish have similar genes."
It's not just a matter of labels. We can imagine a world in which every creature was a unique random mishmash of features without regard to any other creature. Empirically, we do not live in such a world; in our world, living organisms come in definite clusters with regularities to their properties. Evolution provides an explanation of why biology does objectively possess this feature.
I understand that. That still doesn't mean Plato was in a position to be asking a question that requires understanding of evolutionary theory to answer. His question is not much different from him asking, had he lived in the world you posited, why all aerofauns are similar, where "aerofaun" is a label they innocuously came up with for "any creature that flies". In that case, as in the actual one, there are huge differences among the aerofauns, more so than there are among dogs or among flying creatures in this world. But, even if that world's true explanation were "aliens regularly send their randomized automaton toys to earth", that still wouldn't mean you need aliens to answer the aerofaun question, because your question is already dissolved by understanding your own categorization system. Edit: To further clarify the point: In your hypothetical world, the correct (informative, expectation-constraining) answer to a Plato asking "Why are all aerofauns similar?" would be: "They're not similar in any objective sense. They simply have one particular similarity that you deem salient -- the fact of their flying -- and this is obscured by your having been accustomed to using the same label, 'aerofaun' for all of them. And the reason for a word's existence in the first place is because it calls out a human-relevant cluster. Because it matters to humans whether an animal flies or not, we have a word for it. But once you know whether an animal flies, there is no additional fact of the matter as to why the fliers are similar -- that similarity is an artifact of the filtering applied before an animal is called an aerofaun." Similarly, you should answer Plato: "Dogs aren't similar in any objective sense. They simply have a few similarities that you deem salient -- how they're adaptable to humans, work in packs, walk on four legs, like meat, bark, etc. -- and this is obscured by your having been accustomed to using the same label, 'dog', for all of them. And the reason for
I agree with Silas. Talk of genetics and evolution here makes it look like Plato was actually concerned about dogs but that's just an example of the problem. Plato was talking about the general question of which the following are also examples (tokens actually!), "Why do all triangles resemble each other?" "Why do all storms resemble each other?" "Why do all performances of Oedipus resemble each other?" and so on. And he's not looking for a causal explanation, he's trying to understand what our categories are doing and what it means to refer to different things by the same name. Understanding how the human brain clusters perceptions helps us understand the question but it doesn't really answer it- it just transforms it to a question about the reality of such categories. And this problem is far from solved. In any case, if we're counting philosophical problems which were transformed at some point into scientific problems then we might as well include the entirety of the sciences save Geometry, Music and Rhetoric as "solved philosophical problems". I don't say this to condemn philosophy either, on the contrary it was often philosophers who developed the methodology to answer these questions.
Well, I think that's giving Plato too much credit -- my claim is that, at the time, they weren't even aware of how their categorizations were influencing their judgments. But your comparison to the triangle question is very apt. According what I read in Dennett's Darwin's Dangerous Idea, the Western ontology from Greeks through to the 19th century was that all animals represent a special, ideal, "platonic" form. To claim, as Darwin did, that animals changed forms over time sounded to them, like it would sound to us if someone argued, "Okay, you know all those integers we use? Well, they weren't always that way. They kinda changed over time. That 3 and 4 we have? See, they actually used to be a 3.5. Then over time it split into 3.2 and 3.8, eventually reaching the 3 and 4 we have today." In short, the Greeks didn't recognize the hidden inferences that words were making and thought they were finding objective categories when really they were creating human-useful categories. EY goes into detail about this in the article AnnaSalamon referenced, Words as Hidden Inferences.
So what I think you're saying is that Plato had so much map-territory confusion that what he had to say about forms isn't even a meaningful question. Is that right? I might agree. It's hard to figure out how ancient philosophers were actually thinking about problems given that we only approach their work through modernized translations and with our own concepts and categories at hand. I'm not sure I see Plato inferring from words, though. Maybe you can point out that step explicitly? Part of the problem is that "Words as Hidden Inferences" doesn't make that much sense to me as it stands, particularly as it relates to Greek philosophy. Eliezer's example is at the very least poorly chosen. Aristotle didn't even necessarily believe that humans are mortal, he seems agnostic on that question. The quote "All humans are mortal, Socrates is a human, therefore Socrates is mortal" isn't an argument for anyone's mortality. It's an example of a logical syllogism. "All humans are mortal" and "Socrates is a human" are just premises designed to illustrate the form. They might as well be made in set notation. Aristotle believed bodies inevitably die, if I recall. That maybe a wrong judgment but an inference based mostly on observation (or at least based on general theories which were based on observation but unfortunately not much experimentation). He thought that the part of the soul that thinks might be able to live on after the body but that at least some of the soul was dependent upon the body (note that Aristotle's soul isn't at all like the Platonic/Christian conception we're familiar with and could charitably but plausibly be updated into something people here would be comfortable identifying as a person sans body).
No, I agree there was a meaningful question there: "why have the things we (historically) labeled as 'dogs' seem so similar to us?" And you can meaingfully answer that question, in a way that improves your map of the world, by looking at how things got into the dog category in the first place, and why that category (regardless of name) even exists. While I admit I don't have special expertise on Greek philosophy in this area, I do know that they had not gathered enough evidence at that point to even be asking questions that require knowledge of evolution to answer, and that they were hung up on idealism (as opposed to nominalism) which forces you to think in terms of ideal forms rather than models that identify relevant clusters. So perhaps EY's characterization of the situation misled me, but the essential features are still there to support my claim that Plato went astray by not recognizing the source of the classification-as-dog.
I see. I guess we were disagreeing with Anna for somewhat different reasons. Your point is that when Plato was considering the question "why do the things we call dogs resemble each other" the concept the English word dog references was just a folk concept that was applied to some things that looked the same- the causal-historical story for how those things came to look the way they do is irrelevant to the fact they're called the same thing just because our brains classify them the same way. I think thats right. My point was that Plato didn't really care about dogs so much. What he cared about was this phenomenon of resemblance. The question wasn't so much how did discrete individuals (Lassie and Snoopy) come to exist in a way that resemble each other. Rather, the question is "We call both Lassie and Snoopy 'dogs' and yet they are different individuals. What then is the relation between 'dog' and Lassie/Snoopy and what are we doing when we call both Lassie and Snoopy dogs? But that might be more the entire tradition of Western philosophy talking rather than Plato himself. Plato's answer though is that there are abstract objects, "forms" which are imperfectly instantiated in Lassie and Snoopy. Both approximate ideal 'dogness'. For Plato it was these forms that were 'most real' so to speak because they were eternal and perfect. Plato, and especially some of his later followers got really mystical about all this and it got imported into Christianity. But we can excise the mysticism/silly talk about perfection and get a live philosophical question (the most notable Platonist of the 20th century is Bertrand Russell). A modern version of the question might be "what is the ontological status of abstract objects?" At best evolution and genetics are only tangentially involved with that question and only for a subset of abstract objects (things like species) and as a whole the question is generally considered unsolved. As it stands nominalism and Platonism have about equal
These appear to be things that, once solved, aren't "philosophy" any more. So what's philosophy? What, in your view, is left?

Philosophy consists of the questions that we don't understand well enough to even know how to go about answering them, but which, despite that (or because of that), are still really fun to argue about endlessly even in the absence of any new insights about the structure of the problem.

(Basically, I think describing a given problem as "philosophical" is mostly mind projection; from history, it seems that all the qualities that make a given problem a philosophical one have been properties of the people thinking about it rather than of the problem itself.)

Problems we don't know the right questions for yet. When we have a good handle on a question, it becomes science. When we have a good answer for the question, it becomes settled science.

Er... I think a small number of people have made some progress, and I guess you could call that progress 'good chunks', but I get the feeling that the vast majority of rationalists are very confused about the first two questions (or would be if they noticed their confusion). Atheists and theists are both right and wrong in their own way, but neither have a solid understanding of the important underlying considerations. If you asked me if souls are real or if God is real, I'd say yes to both, but the explanation thereof would be excruciatingly difficult, and I'd be tempted to label the question 'not even wrong', akin to 'If a tree falls in the forest...'. (And I'm not talking about trivially true ensemble universe stuff, either -- I think there's more to it than just being smugly meta-contrarian.) Your point stands that there are a lot of solved philosophy problems, I'm just disputing your first two examples. Free will is a good example, though.
Not to make things 'excruciating' for you but you can't really leave that hanging.
Gah. I'll stick my neck out a bit. Short barely-defensible version: sometimes your low-level-language/ontology should be bits, sometimes it should be gods. Souls are a pretty good model of how memetic cognitive algorithms make up about half of human experience and don't reside in any one body. (You could remove all of the memes from someone's body and put them in someone else's body, and that'd be damn close to reincarnation. There are obvious objections here but I'm just going to plow ahead.) For instance, Wikipedia: "In philosophy of mind, dualism is a set of views about the relationship between mind and matter, which begins with the claim that mental phenomena are, in some respects, non-physical." 'Non-physical' is the key concept. I like to model cognitive algorithms in terms of e.g. memetics and computer science and phenomenology, not in terms of atoms. So when the nasty monists come along and say 'everything about this soul business can be explained in terms of atoms', I say, well sure, the languages are Turing-equivalent, but who cares? There's barely a difference in anticipated experiences, it's just arguing about which ontology better carves reality at its joints. Personally, I'm just fine with using the ontology of souls and gods and magic. Yeah, half of it 'reduces' to the placebo effect and memetics and what not, but why choose that ontology? Use ontological pragmatism. (I guess there's an argument that you can have a speed prior over speed prior languages and should use low-level languages when all else is equal, but I find 'algorithmic ontology' to be simpler and easier to reason about than 'atomic/physical ontology' anyway, so once again I think I disagree with the monists.) With regards to God in particular: God exists in a lot of peoples' heads. He's a massively parallel distributed cognitive algorithm that millions of people use and model. That's more of an existence than your average person, by far. What atheists mean when they claim He doesn't

With regards to God in particular: God exists in a lot of peoples' heads. He's a massively parallel distributed cognitive algorithm that millions of people use and model. . . . In that sense, and it is an important sense, God is very real. More than that, all memes (memetic algorithms) are real.

But that's not the sense that theists mean when they say "God is real", and it's definitely not the sense that atheists mean when they say "God isn't real". When someone says "God isn't real", it's not like they're saying that God is not a meme that exists in anybody's mind — a person needs to have their own mental copy of the God algorithm, and the understanding that millions of people share it, in order to even bother being an atheist. It's pretty clear that they mean that the God algorithm isn't a model of any actual agent that created the universe or acts on it independently of the humans modeling him.

So I'd disagree with "In that sense, and it is an important sense, God is very real." Clearly in that sense God is real, but it seems like a profoundly unimportant sense to me, particularly because I don't think anyone actually uses "real" that way. It seems like a type error; a god is an extremely different sort of thing than the idea of a god.

Indeed. God is the omniscient, omnipresent, infinitely powerful and utterly non-existent creator of the universe! Cognitive algorithms are cognitive algorithms. Sometimes they make people say the word 'God'.
You're right. I suppose I'm just ignoring the unimportant senses because I'm talking to rationalists about what 'God' could be thought of as, and, well, the other more common ways of thinking about it don't convey much information. I was mostly trying to convey an ontology of cognitive algorithms, but got sidetracked into talking about this God business via a request from the audience. I honestly don't care much about how typical theists or atheists use the words, because, well, I don't care what they think. ;) I think I managed to get my points across despite defecting in the words game. Still, my apologies. Also something very much like the actual God exists in a Tegmark multiverse, but that's also pretty unimportant, decision theoretically speaking. He's just another counterfactual terrorist.
Really? It sounds kinda like a self-defeating object. My guess is that there is an unending infinite hierarchy. But I don't trust my intuitions about the large scale structure of the multiverse much.
Sure. And in that sense, Santa Claus is also real, and it's entirely correct to say that "God is no more real than Santa Claus." Or have I misunderstood you? And yet, I suspect few theists would agree with that statement.
Allow me to link to this post on the social construction of Santa Claus
I wouldn't say that's entirely correct. God is significantly more real than Santa Claus. He's inspired all kinds of art and science and devotion and what not, to a much greater extent than Santa Claus. Plus, people don't really talk to Santa Claus, whereas they often talk to God, and sometimes He answers. God is a much more complex algorithm. Theists wouldn't agree with your statement, but I wouldn't either. And there are lots of statements that are true that theists would disagree with, just like there are lots of statements that are true that anyone would disagree with, because people suck at epistemology. But that's kind of tangential to the main thrust of my argument.
I'm a little startled by you interpreting "more real" as an quantitative comparison, when I meant it as a qualitative one, so I have to back up a bit and ask you to unpack that. Presumably you aren't arguing that inspiring art, science, devotion and whatnot is what it means to be real, or it would follow that most of the atoms in the universe are non-real and are in non-real configurations, which is a decidedly odd use of that word. You say later that God is "much more complex," and I can't really see what that has to do with anything... I mean, a tree is much more complex than a wooden pole, but I wouldn't say that has anything to do with the reality of a tree or of a wooden pole. Basically, I can't quite figure out what you mean by "real," and you seem to be using it in ways that are inconsistent with the way most people I know (including quite a few theists) would use it. For my own part, what I would conclude from your argument is that God, independent of reality or non-reality, is more important than Santa Claus. Which I would agree with. If God is a reality, it's a more important reality than Santa Claus. If God is a myth, it's a more important myth than Santa Claus. Etc. Incidentally, many people write letters to Santa Claus, and sometimes things happen that they experience as a reply from Santa Claus. If that is different from what you are referring to as an "answer" here, then I've continued to misunderstand you. So, let me back up and try again. I'm currently imagining a purple dinosaur named Ansel with a built-in helicopter coming out of its skull and a refrigerator in its belly. Are you suggesting that Ansel is real, since it exists in my mind, and that it would become increasingly real if other people sat around imagining it too?
Yes. And if I imagined Ansel except green and not purple, then that adds a little bit to the realness of Ansel, unless we want to call the new green dinosaur Spinoz instead and have it be its own distinct cognitive algorithm. Nah, I reason about it in terms of measure. You have one cognitive algorithm that's being run on one mind. You have another cognitive algorithm that's running redundantly on a hundred minds. I'd say the latter has about a hundred times as much measure as the former. I don't know how else to reason about relative existence. (Realness?) I'm porting this sort of thinking over from reasoning about the universe being spatially infinite and there being an infinite number of TheOtherDaves all typing slightly different things. Some of those TheOtherDaves 'exist' more than others, especially if they're doing very probable things. If existence isn't measured by number of copies, then what could it be measured by? The alternative I see is something like decision theoretic significance, which is why I was talking about what you called 'importance'. But I'm wary of getting into cutting edge decision theory stuff that I don't understand very well. Instead, can you tell me what you think 'realness' is, and whether or not you think God is real, and why or why not? We're starting to argue over definitions, which is a common failure mode, but it's cool as long as we realize we're arguing over definitions. I think that everything exists, by the way: there's an ensemble universe, like Tegmark's level 4 multiverse, and so we can only quibble about how existent something is, not whether or not it exists. I might be having trouble trying to translate commonsense definitions into and out of my ontology. My apologies. I mean that people tend to use a lot more neurons to model God than to model Santa Claus, and thus by the redundant-copies argument hinted at above this means that God exists more. Relatedly... You're right, I forgot about this. Parents have to use l
I wonder whether you could comment on, and compare, the following statements: * God exists. * The "monster" sporadic simple group exists. * A non-trivial root of the zeta function not on the critical line exists. * A proper factor of 101 exists. * Components of an alien spacecraft that crashed in Roswell NM in 1947 exist (at Area 51 of Edwards AFB).
I don't feel qualified to answer. If we're talking about exists in a mathy sense, then any of those that can be represented mathematically exists. I'm not sure if there are universes where 5=4, and other logically impossible things. I've heard arguments to this effect but I don't remember what they are. Surely you can have things that appear logically impossible, due to hiding some contradiction in the middle of a titanic proof, but actually logically impossible, I don't know. 'God' is vague because 'omnipresent' and the like don't really make sense; similar problems with proper factor of 101. The last one about Roswell seems obviously true, it's just not true in most universes we find ourselves on. But I mean, it's a true statement in a trivial way. 'We live in a spatially infinite universe and so there exists a copy of you that is the same in every way except with 20 foot long hair' is also trivially true. But if you only care about worlds in which your hair is 20 feet long, then all of a sudden its truth is not trivial; it's vitally important. What implied questions did I miss?
I was trying to tease out whether your "God is real" is intended in the same sense as "the monster group exists" - neither exists in physical reality, but both exist in at least some minds; in a kind of mental reality. My other questions were intended to ferret out whether your idea of a mental or algorithmic "real" includes only well-defined and consistent ideas, or whether vague, incorrect, and impossible ideas also qualify as "real" in your sense. Sorry I didn't make that clear in the original comment - I didn't mean to seem confrontational. I'm just trying to get a better understanding of your interesting suggestion. This appears to be one situation where more politeness might have helped. :) As for where I am coming from, I'm one of those philosophical anti-realists mentioned earlier in this thread (and a big fan of van Fraassen). I am far from convinced that electrons are real. So I'm interested in the details when someone says, in effect, that God is just as real as electrons.
What's the usefulness of "I think that everything exists, by the way: there's an ensemble universe"? How does it constrain your expectations? I don't see how having specific beliefs either way about stuff outside the observable universe is useful. Now, if you can show that whether the universe beyond the observable is infinite or non-infinite but much larger than the Hubble Volume constrains expectations about the contents of the observable universe, then it might be useful.
Off the top of my head: If the world is very big then there are more agents to trade with or be simulated by. Also I'm not sure what counts as the observable universe -- we can't see beyond the Hubble volume with our telescopes, but we can probabilistically model what different parts of the universe or different universes look like nonetheless. We also do not know what is ultimately observable. We currently lack the ability to observe mental phenomena but I still have specific beliefs about roughly what we'll observe when we really understand consciousness. It is useful to be curious about mysteries to which you believe there to be no answer; beliefs like that often turn out to be wrong.
OK, I think I'm following you now. And, yes, we were talking about definitions: I wanted to make sure I understood what you were actually saying before I tried to respond to it. I think we label something a "real X" to assert that it implements a deep structure that characterizes X, rather than merely having a superficial appearance of X. For doing that to be meaningful we have to be prepared to cash it out in terms of the deep structure we're asserting; if we can't do that then we don't mean anything by the phrase "real X." When someone says "Y is real," I try to interpret that to mean "Y is [a real X]" for some plausible X. If someone says "The elephant I'm seeing is real," I probably understand them to refer to (I1) a real elephant, which implies that it has mass and occupies volume and reflects light and radiates heat and so forth. If they mean I1, and it turns out that what they are seeing doesn't have those properties, then they are wrong. If they meant, instead, that it is (I2) a real activation of their retina, then questions of mass and volume are irrelevant... but if it turns out their retina isn't being activated, then they're wrong. If they mean, instead, that it's (I3) a real activation of their visual cortex, then questions of retinal activation are irrelevant... but if it turns out that their visual cortex isn't being activated, then they're wrong. Regardless of whether they're right or wrong, these are all different claims, even though the same words are being used to express them. If they mean I3 and I understand I2, communication has failed. If I've understood you: if I say "God is real," you understand that to mean (J1) my neurons are being activated. And J1 is certainly true. But if I meant to express something else (J2) which implies the entity responsible for the creation of the universe once split the Red Sea in order to allow my ancestors to escape from the Egyptian army, then communication has failed. Sure, we can get along just fine
By the way, User:ata made this illuminating comment which I agree with; see my reply (where I admit to defecting when it comes to using words correctly).
(nods) Cool. This is essentially why I have been talking all along about the use of words, rather than talking about what kinds of things exist; it has seemed to me that our primary point of discontinuity was about the former rather than the latter.
By "real" I'm assuming you mean something like "a phenomenon that needs to be accounted for in order to make accurate predictions". Specifically, predictions about what people will do. If so, absolutely. Of course then there are other valid senses of "real" which everyone else is arguing below, in which there is the question of effects outside people's actions, and whether the phenomenon showed up in people's heads because an entity outside our scientific understanding called God put it there. Those are, of course, the tricky ones. (God of the Gaps time!)
Having read your explanation, I think you ought to say both are not real. Your description of God and souls as parallelized cognitive algorithms does not predict what "God is real, souls are real" predicts. I think it would be more accurate to say "the belief that 'God is real, souls are real' is definitely real, and regardless of the truth value of the statement, the belief itself affects the world". That makes the same predictions as your cognitive algorithm idea (which I quite like), but doesn't cause misunderstandings with people who are using the word 'real' in very common ways.
What about the virtue of narrowness?
Being narrow with your own conceptual framework is good, but I'm promoting being liberal when it comes to interpreting others' concepts, when playing fast and loose in back-and-forth discourse, and when reasoning very abstractly in order to see connections. As long as you make sure to go back and make sure that everything connects precisely, and avoid affective death spirals around seemingly big insights about the fundamental nature of all things (which is somewhat difficult), it can be useful for getting new perspectives and for communicating concepts effectively. ETA: With regards to communication, this only really works if each of the participants has some amount of faith in the epistemology of their conversation partner. If some random guy told me God exists, and I wanted to make him smarter, I wouldn't go on about all the ways that God exists; I'd go on about the ways He doesn't.
Or just teach him the Virtue of Narrowness.
True, that's a better solution. But, but, but being contrarian is so much more fun!
You should only be liberal in what you accept, if you can transform it so that when you repeat it, you can still be conservative in what you say.
When possible this is best, but some people at SIAI (cough Vassar cough) have conversational styles that are very fast so as to convey the most information in the shortest time, and it's hard to do real-time transformations from ultra-abstract statements to reasonably-precise internal models and back as information is exchanged and people build up their ontologies on the fly. (Which is pretty awesome when it happens -- one of the joys of being a Visiting Fellow. And of talking to Michael Vassar.)
I'd more or less agree with this, but would add that it's important to flag the difference between asserting the existence of X, making decisions based on the existence of X, and supposing the existence of X. If I start using language in a way that elides those differences, I am doing nobody any favors, least of all myself.
I think a good working definition of philosophy is "not science yet" - so the answer to this question is "yes, but we don't call it philosophy any more".

There's a famous quote by Ian Hacking regarding electrons - "If you can spray them, they're real".

In "disguised query" terms, this corresponds to "can X be reliably used to effect changes on the rest of what I consider 'real' already?"

We know that relativistic time dilation is real, for instance, because you have to take it into account to build GPS devices that work as expected, and these are as real as they come - you use them to drive your car somewhere.

This seems like the best criterion for reality: once you have something (like a GPS receiver) that cannot be explained or built without the understanding of relativity/atoms/luminiferous aether, then you can consider them to be "real". (This is a sufficient condition, but probably not a necessary one.)
Did I say GPS? Man that's exotic. Apparently car batteries depend on relativistic effects.
I don't think this counts, in that the predictions of relativity were not needed in the design. Relativity is needed to explain why certain phenomena crucial to the design occur, but the phenomena themselves were already known at the time of design. Another similar example is that relativity is needed to explain the color of gold. If all the evidence you had for relativity was of this form, and then it turned out relativity was wrong, you wouldn't be too surprised - you'd have gotten your theory wrong, but you wouldn't be saying "How the hell can batteries work, then?!" You still wouldn't know how car batteries worked, of course, but it wouldn't seem impossible that they should work, since they were based on phenomena known prior to relativity. By contrast, learning that relativity was wrong should make GPS seem impossible, since relativity was needed to predict that it would work (in its current form, with the relativistic calculations included) in the first place. (Here of course by "wrong" I mean "significantly off in these situations" rather than just "not literally true".)

The MWI people like to cite Real Patterns by Daniel Dennett. I also wonder what LWers think of structural realism.

This seems like a pretty good idea. It suggests that the "reality" of a theory is point on a continuum, not a binary property. For example, under this interpretation, I'd say Newtonian physics is pretty real, but Relativistic physics is even more real than Newton's physics.

The "reality" of a theory is a point on a continuum of how well the theory maps to reality? After accepting that reality is external and objective this seems like the best definition. How well a theory maps to reality can be hard to measure until a better theory comes along however. The real problem is that through out history and to the present day people jump to conclusions and call things real with out proper evidence. If scientists had not jumped to conclusions in the 1860s then there would have been no debate over weather atoms were real or not.

By the mid sixteen century, it was clear to the astronomers at the University of Wittenburg that Copernicus’s model was useful. It was easier to use, and more theoretically elegant, than Ptolemaic epicycles.

Copernicus's model still had epicycles. He improved on the Ptolemaic model by dropping the equant.

I realize that. But his epicycles were still easier to use than the Ptolemaic epicycles model.
I'd consider mentioning the equant as the elimination of it seems to be where most of the theoretical elegance was gained. There were fewer epicycles (were they used differently?) but I'm not sure how much of the epicycle elimination was due to genuine improvement and how much just left the theory as less accurate (more epicycles usually means more precision).
In what sense were they easier to use?
Well there were fewer of them... but Anna may mean something else.

Are atoms real? Whatever the answer to that question is imagine if it were exchanged, that is suppose that magically the reality of atoms became unreal or the reality of atoms became real, would the world be in any way different as a result? I think the clear answer is no, therefore regardless of what the status of atoms may ultimately be, the question "Are atoms real?" is not real because real things make a difference and unreal things do not.

John K Clark

0Ronny Fernandez12y
If I thought that atoms were unreal, I would not expect to be able to photograph them. I also wouldn't expect a single atom to be capable of casting a shadow. That's some ways (and there are many more) that I could be wrong about atoms being unreal mere pedagogical tools.
Could you give me an example of something that is real?
Whatever substrate supports the computation inscribing your consciousness would be necessarily real, under whatever sense the word "real" could possibly have useful meaning. ("I think; thinking is an algorithm; therefore something is, in order to execute that algorithm.") Interestingly, proposing a Tegmark multiverse makes the deepest substrate of consciousness "mathematics."

This is an extremely thought-provoking article that I haven't been able to get off my mind, so thanks.

I think we can all agree that reality (the 'territory') as a whole is real, but this is nigh-tautological. The question of whether a particular concept is a true part of reality (e.g. atoms) is more interesting but not as straightforward.

jsalvatier suggests that 'the "reality" of a theory is point on a continuum, not a binary property', and it seems there's something to this. My gut response to the question of 'are atoms real?' was 'of course! we... (read more)

For some reason, this sentence struck a chord with me and made a number of somewhat confused thoughts fall into place (a mini-epiphany). Indeed, real means the territory, whatever that is. I could have consoled myself in moments of panic fearing that reality wasn't really 'real'. However real reality feels, there isn't something else 'more real'. So what did I mean when I felt that reality didn't feel real? Thinking about it for a few moments, 'feeling real' subjectively means not only empirically based (seeing it, touching it, hearing it) but that the sensory information is integrated and familiar. A very new environment, a chemical imbalance in your brain that make it difficult to process sensory data and even an inner ear infection all cause feelings of unreality. Something abstract, likewise -- "a mother's love", for example -- can be considered subjectively real, if you have lots of familiar and empirical examples of such love (she held me, she drove me to school, I had happy feelings). I don't know if this feeling of "real" isn't just an analogy your brain makes. That is, that it feels integrated on all sensory levels and familiar like a familiar physical object. Finally, by analogy, atoms and photons should subjectively feel real for someone studying them if there is a lot of integrated empirical evidence of them and they are familiar objects. Thus the subjective feeling of something being real is scalable: they feel somewhat real if you can see their effects, but more real if you can see/hear/touch them directly. And then regardless of the kind of empirical evidence, it'll feel more and more real as you become more familiar with them. All of this is relevant to the post only to the extent that the statement, "X is real" has a subjective component.

When I hear "Are atoms real?" I imagine zooming in on some object until I can see an atom. Could they just be asking if, given the technology required to magnify/compress/measure some form of sensory input about something, it would make some kind of intuitive sense to a human brain?

Like, if you could stand above the solar system and look down on it, the Copernican model would say it makes more sense to hover over the Sun and imagine everything rotating around you than to hover over the Earth and imagine everything rotating around you while piroue... (read more)

This is an interesting point. What does "more sense" mean? From a purely utilitarian point of view, Tycho Brahe's compromise system is as useful as Copernicus's: it gives the same experimental predictions while still keeping Earth at the center of the universe. Kepler's acceptance of the Copernican system had more to do with his Pythagorean views, his perception that the center of the universe must contain the Central Fire, the cause of all motion. In other words, we're dealing with subjective views here. And yet it objectively seems to make more sense to center the Solar System around the Sun. Perhaps because there is no reason to privilege Earth above the other planets, and no reason to assume that the Sun "really" revolves around, say, Venus?
Lets go with "more sense" = simpler. They both provide accurate predictions, but the heliocentric model that gravity holds the Planets in orbit around the Sun has a lower Kolmogorov complexity than a geocentric model in which the Earth is central, but everything has weird complicated paths as they orbit.
Are you comparing the Copernican system or the Keplerian system? The straight Copernican system is about as complicated as the geocentrist system. You only get the reduction in complexity when you go for full out Keplerian. And note that there were other pre-Kepler systems that were arguably simpler than the Copernican system. this article gives a good brief summary.
My mistake. I was thinking of Keplerian when I wrote this.
Interesting idea, but it seems a little badly-defined. Some aspects of quantum physics don't seem intuitive to me (mostly small details). Does that mean that those details aren't "real" to me, but they are real to other people?
In a nutshell, yes. That doesn't make reality subjective, it just means that different people hold different things as real. I'm pretty sure that given a long enough conversation, people would agree on if something is real enough. To clarify the definition, I'm basically reading the question and post as "Are electrons real objects?" Most of the examples given were about objects, or easily observable things about them, like what's going around what. Its less of a question of being intuitive, and more one of whether it would be observable given basically magical senses. This dissolution doesn't really hold that well for theories. I can be convinced that things are true (like the early chemists who see atoms are yielding good predictions, but not necessarily existing), but without knowing if they're real. Something that illustrates this split nicely is the question "Is Heisenberg's Uncertainty Principle real?" Its certainly true, you can't be sure of a particle's position and momentum because as you shorten a photon's wavelength enough to make the position more certain, you increase the photon's energy and make the particle's momentum less certain. When I learned that, I felt jiffed. "Hey!" my reality-asserting subroutines complained to me "That's not uncertain at all! It happens to be that in real life you can't be certain, but if I could observe a particle without light or interacting with it any way using some magical impossible version of sight, it would totally have a definite momentum and position!" It wasn't until the teacher demonstrated the unit rearrangement to phrase it in terms of energy and time, and talk about particles going through things that they didn't have the energy to penetrate for me to be convinced that it was real, and not just an accurate theory.

Another way to state your conclusion is that the "is it real?" question reduces to the question of whether a model yields a Level 1 or Level 2 understanding [/self-promotion]. Indeed, those concerns where part of what motivated me to create the hierarchy.

The atomic theory seems to me very different to me than the others, which seem more like the motivating example. The atomic hypothesis also seems much easier. In particular, I think everyone was in agreement about what it would mean for atoms to be real or not, whereas in the other examples I think that there was no such agreement.

It is true that that the debates used the dichotomy "real or just a useful tool" that appeared in the other examples. Yes, what they meant by "real" was "is it useful in a less circumscribed setting,"... (read more)

This is rather tangential, but it's something about geocentrism that has been bothering me recently. Aristarchus (c 250 BC) and Hipparchus (c 150 BC) computed that the sun has 10x the diameter of the earth and thus the earth should circle the sun. Their contemporaries said: no, heliocentrism implies that the fixed stars are very far away. That's an OK argument against heliocentrism, but did they really engage with the intermediate step? [see update] Ptolemy agreed that the sun was 10 million kilometers away, but did he discuss its size?

And what did later a... (read more)

Why can't real-ness just be functionality? People often resist this concept, but it seems sensible to me.

Exploring the function of things, in fact, how we know about the universe - when we talk about what something is, we'll really talking about an aggregate of functions that it has (e.g. we know that if we do something to a part of the universe, something will happen - since the result varies by the part of the universe we're looking at and the conditions under which we perturb it, we can divide the universe into "things.") We can say that ato... (read more)

Aether not only correctly predicted that light would act as waves, but also incorrectly predicted that the Earth's motion with respect to aether should affect the perceived speed of light.

I don't know anything about old ideas about aether, but I've wondered why it was wrong, and whether the aether-idea is really conclusively wrong or whether someday science could return to that idea.

Does "aether" necessarily mean that the observed speed of light may vary? In particular, what is packed into the word "aether" that demands this?

...I'm ... (read more)

The photon waveform has actual mass, and it certainly makes waves when light is traveling. As such, calling the photons themselves aether doesn't seem that inaccurate.
I suppose no one has answered my question above because no one (yet) has a handy list of the essential, minimal assumptions of the theory of "luminiferous aether". Though perhaps I didn't describe my question well enough. It was: What assumption about the aether caused it to be disqualified? During my drive home, I had some time to recall my motivations for wondering about the theory of aether and whether it is really dead or just out of style.. From what I understand of what light is -- mainly from discussions here on Less Wrong -- light is what happens as the electromagnetic field gets updated. Suppose you have an electron at location (x,y). This creates an electromagnetic field centered at (x,y). Then you move the electron to position (x',y') and the new electromagnetic field is centered there. The whole electromagnetic field has to shift by this much. But the field can't shift throughout the whole universe instantaneously. The change in the electromagnetic field propagates at a finite speed from the new position. We see this 'fixing' of the field as a light wave propagating through space.* Naively, I view it as a disturbed mesh that rights itself one kink at a time. Is this mesh 'real'? If it's not real, what is the electromagnetic field? What is changing and getting fixed over time? To me, the question of whether the aether is real is the same question. Isn't there something there? But if not, how can it work?? I don't mind if the answer is something more abstract than a type of matter/particle. It just seems that if information is moving something must be carrying it. * We see a lightwave by catching it, which means we change the electromagnetic field in exactly the right amount to counter the defect and stop its propagation.
I think this gets back to the question of what you mean by "there". Because if I have, say, water in a tank, and I move around a stick I placed in that water, then the 'water field' (or whatever I want to call the positions of the water molecules) will update based on that, and it will update at a finite speed because the information is carried by traveling water molecules. So the water field is there because water molecules are there- if you put something in their way, they'll run into it. But electromagnetic waves are carried by photons, which are really weird. Water molecules have a rest mass- if you managed to slow one down to no speed at all, it would exert about as much gravitational pull as normal, and it would still get in the way of other things you tried to push through it. A photon has no rest mass, and a way of thinking about that is to say that if the photon isn't moving, it isn't there. And so if by "thereness" you mean "if I shoot a neutron at a stationary one, is the neutron sometimes deflected?" then water molecules are there and photons aren't. But there's another sense that we can talk about thereness- what happens when we (or they) speed up. If I had the aforementioned water tank on a train moving near the speed of light, things would look the same inside the train- but really weird from outside. To observers, the ability of the 'water field' to update depends on how fast the water field is moving relative to the observer- but that isn't true for the electromagnetic field. All observers see it 'updating' at the same rate. So, what do we mean by "aether"? Here, I think we might be getting in a linguistic/historical issue, which is what you originally asked about. I was fascinated, watching a talk between PZ Myers and Dawkins (one of those, might not be the first one), where for Dawkins the phrase "group selection" seemed to be irretrievably connected with Wynne-Edwards, despite there being several defensible things that also have a connection
Theory of æther was disqualified because of relativity. If there was some real mesh, its nodes would have to be located somewhere, and we would be able to measure our velocity relative to it. It does not work that way. The way it works can still be described by æther, but one must postulate that time and distance measurements are distorted depending on the velocity with respect to the æther, and still one has no chance to determine in which inertial system the æther is stationary. This is not how real entities behave.
Well, I specified "luminiferous" (light-bearing) aether in the title, although I abbreviated this as simply "aether" in the rest of the section.
In the above, please consider "aether" replaced by "luminiferous aether". I suppose 'aether' could be vague enough to mean anything, and in that sense may be real, but I am curious about what aether needed to be in that particular theory in the 1800s.

It looks like you dropped a word:

Despite this usefulness, there was considerable (debate?) as to whether atoms were “real” or were merely a useful pedagogical device.

Thanks. Fixed.
Another one: I finished reading, so that should be the last one. :)
Why do you communicate things like this publicly? It takes other people's attention, even if for a bit, where there seems to be no reason whatsoever for that to happen. It's an error that costs you and others almost nothing, but an error nonetheless.

Benifets of making public proofreading comments include:

Because I also check to see if anyone else has made a comment reporting the same error, it prevents the writer from getting many messages for the same correction.

When people see the comment and a polite reply from the author reporting the error has been fixed, it encourages them to report proofreading errors that they see, instead of saying silent, improving general quality of published articles.

This doesn't really apply in this case, but sometimes when a proposed correction resolves confusion generated by the error, the proofreading comment can help other readers to understand before the author responds and fixes the mistake.

I agree that due to being a distraction after the error is fixed, this is a tradeoff, and I would like to reduce that effect, perhaps a way to tag a thread as "resolved proofreading issue" that would collapse it be default or sort it to the end.

Kuro5hin, a general-purpose discussion site that's since been taken over by trolls, had a mechanism like this. When submitting a top-level comment, you could mark it as "editorial", which would keep it hidden under default view settings. This trick worked pretty well, and I notice that K5ers seemed more eager to offer editorial suggestions than LWers.
Thanks, I see now how it is less settled than I believed.
In my case it's a compulsion. No cost-benefit analysis is involved.
I suspect it's for the same reason I occasionally litter by accident and not pick it up; it's a negative externality but the cost of self monitoring all the time is greater. I'd get worried if it goes over a (small) threshold. People like the communication for non-informational reasons and occasionally speech-litter.
Thanks again. I guess I should proof-read more carefully.

Hrm... I'd say atoms are real iff reality (whatever that is) obeys a certain set of (approximate) regularities (that basically amount to the rules for atoms). ie, there's a sense in which they're "actually there"

The atoms are an explanation for a phenomena iff the fact that those particular regularities are largely sufficient to explain the phenomena in question. That is, that one doesn't have to "dig deeper" to still explain things.

(Of course, if atomic theory in general had failed and only explained a single particular thing, that would suggest that the first criteria was violated.)

Lorentz, not Lorenz.


[5] Thus, to extend this conjecturally toward our original question: when someone asks "Is the physical world 'real'?" they may, in part, be asking whether their predictive models of the physical world will give accurate predictions in a very robust manner, or whether they are merely local approximations. The latter would hold if e.g. the person: is a brain in a vat; is dreaming; or is being simulated and can potentially be affected by entities outside the simulation.

Hmm. Let's say we live in a multiverse where there are infinitely many unive... (read more)

I'm not sure what point you're trying to make, if you're trying to make one.

One other constructive criticism: why don't you consider some non-examples? I mean, theories that gave good predictions, seemed to generalize, and then, didn't?

I can't think of any stellar examples right now, but the lame example of the black swan comes to mind.

Besides the predictive power as a way to measure "realness", I would add persistence. A car in my dream is less real than a car before me when I cross a street in my daily life, in the sense that it persists more in my mind.

Taboo real?


That sounds like a big step backwards.

Only anti-realists think hidden questions lurk behind the concept of 'reality' [that's a fair definition of anti-realism]; realists take 'real' as primitive. You feel confused because you want an anti-realist account of "real," despite being a realist yourself . (Or else, you're an anti-realist smart enough to see through the extant anti-realist theories.)

Quine's is a famous example of an anti-realist account. Quine said the concepts denoting existing things (those that are real) are those variables you must quantify over in the best scientific ... (read more)

You know Eliezer argues that atoms are not individually real, right?

Not real at the fundamental level, correct, but real in the relevant sense for certain levels of abstraction, and (satisfying the criteria Anna Salamon gave and the and the Level 2 standard I gave) capable of plugging in to other models of reality.
Well, the most famous opposition to atomic theory (famous to me at least) came from Ernst Mach of Mach's Principle. Seems like applying his positivism to quantum physics tells you that only the wave-function and the Born rule "are real". Atoms just give us a convenient way to approximate these rules for predicting experience.
Reductionism sequence). Now. Edit: Okay, maybe later.
Nice edit. :P

How about photons? If they are real can they be particles as well as waves? Feynman (who got a nobel prize for it together with Sin-Itiro Tomonaga and Julian Schwinger (they all thought of it independently)) went for waves. So did he think that for a photon to exist at all it needs to be classified? I think he felt photons were "real" but kind of shady before he nailed them down as waves instead of particles (making them "really real").

Feynman called light particles. (See also this video at 36:15 through 36:30.) And welcome to Less Wrong! Edit: Sorry I don't have an intelligent response to your actual point. For what it's worth, I (as a physics dilettante) think that light is neither waves nor particles, but blobs of amplitude (or something). It certainly doesn't behave like little billiard balls. I defer to Feynman, though.
I remembered it the wrong way around. Feynman (and the other 2) went for particles rather than waves. What I was trying to say is that similar to atomic therory moving from "a useful pedagogical device" (1860) to "atoms really exist" (today), photons went from "this curious thing that looks like a particle or a wave depending on how you set up your experiment" to "It is a particle".
Well it went to "it's a particle" because all the other particles became "excitations of quantum fields" as well... (And there are still significant differences in the phenomenological treatments because the boundary conditions play a very special role in describing and quantizing the field modes in actual calculations.)
In the sense that the word "particle" at that scale now means "quantum probability distribution". BLOB THINGS. (I still visualise atoms as planetary electrons around a nucleus sun - the electrons possibly in shells - until I catch myself and try to visualise s and p shells. Too much out-of-date popular science as a child.)

The map is not the territory. What you think of when I say "atom" is your map. An atom is the territory. What you think of is just a useful device. This applies to everything. Trees, rocks, etc.

I'm not sure that does much to unpack what scientists were investigating, when they held scientific debates about the reality of atoms. Nor to explain what we're trying to ask, when we say "is the physical world actually real?" "In what sense does the world exist?". Humans feel like there's a question there; I feel like there's a question there; but I'm confused as to what exactly I'm trying to ask. It would be nice to dissolve the question, so that there's no blank spot left in my head where "is real" or "exists" used to live. As noted in the article, I'm hoping that looking at specific scientific controversies might be a useful warm-up, and might help more than just remembering that the map is not the territory.
Could you expand on why you feel like there's a question there? What does 'physical' mean? (Is it a distinction between your perceptions being the result of a high-resolution computation where other brains or stars or non-observed phenomena are also computed in detail and sent to your brain and a low-resolution computation where lots of computationally expensive details are left out and replaced with just barely imperceptibly simplistic high-level generators? That is, a physical universe would be detailed/expensive, whereas an... er, algorithmically simple/inexpensive universe would be algorithmically simple/inexpensive (speed prior-wise). Or were you thinking of a different distinction?) For awhile I tried to make a distinction between existingness and realness (everything exists and nothing exists as made clear by ensemble universe theories, but, say, only directed acyclic graphs are real, or only things of decision theoretic significance are real, or what have you), but eventually I felt like I wasn't getting much traction from it. I've had a lot more luck with a distinction between 'right' and 'good'.
What was your motivation for this distinction? Also, can you summarize the progress you made?
Tangentially, the usual distinction is that 'right' applies to actions and 'good' applies to states of affairs, with some slippage.
In person some time, I've already bitten off more than I can chew with my 'memes are real, dualism is correct' meta-contrarianism elsewhere in the comments. Sorry Anna...
I feel like the question there is "Does the map match the territory?" If atoms are real, then there is something in the territory to which the symbol atom on our map refers. I'm tempted to say that if an atom is real, then any sufficiently accurate model must include something that refers to them. However, wouldn't that lead to the conclusion that no, atoms do not exist, we were mistaken? Really quantum wave functions exist, and an atom is just a shorthand for referring to a particular type of collection of electron, quark, and gluon wave functions. (um, oops, exceeded my knowledge of quantum mechanics here, replace what I said with whatever quantum mechanics says an atom is.) Or would it lead to the conclusion that atom is a name for a particular well-defined class of collections of wave functions? If something such as an atom is not real, then they are just a convenient organizing principle that let us achieve a simplified, but necessarily incorrect, model. Whether to keep using the known incorrect model tends to depend on its usefulness, but you must always account for the incorrectness. (For example, we keep using Newtonian Mechanics and the Ideal Gas laws, even though both are known to be incorrect. We just know what domains they are accurate enough in to keep using.)
"is the physical world actually real?"- The words physical and real are very close together in my map and with out know how they are spaced in your map I can not gain traction in helping answer this question for you. "In what sense does the world exist?" In the sense that it is repeatable. I currently live under the assumption that this repeatability derives from the world being external to myself and objective; this map as of yet fits what I have observed of the territory.
That explanation doesn't distinguish between the questions we have about the reality of "trees" and "atoms", the reality of "justice", and the reality of "phlogiston". You're neglecting important distinctions.