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.
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.
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.
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 http://plato.stanford.edu/entries/scientific-realism/ 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.
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 ...
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.
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.
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.
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.
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.
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.
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.
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
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...
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...
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,"...
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...
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...
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 ...
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.
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.
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.)
[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...
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.
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 ...
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").
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.
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.
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.
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.
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.
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...
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.
You're right, I forgot about this. Parents have to use lots of neurons to model Santa Claus when crafting the letters. Kids don't tend to use as many neurons when writing letters to Santa, I think. But add up all of these neuron-compuations and it's still vastly less than the neuron-computations used by the many people having religious experiences and praying every day. (I'm using number-of-neurons-used as a proxy for strength/number of computations.)
Also, 'people' aren't ontologically fundamental: they're made of algorithms too, just like God. So I don't see how you can say 'God doesn't exist' without implying that Will Newsome doesn't exist; Will Newsome is just a collection of human universal algorithms (facial recognition, object permanence) and culture-specific memetic contents (humanism, rationality, Buddhism). The body is just a computing substrate, and it's not something I identify with all that much. And if I'm just a collection of algorithms running on some general computing hardware, well, the same is true of God. It's just that he's more parallel and I'm more serial. And I'm way smarter.
(Not that there is any such thing as 'I'. 'I' am made of a kludge of algorithms, and we don't always agree.)
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.
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:
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".
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.