Hrm.

First, let me apologize pre-emptively if I'm retreading old ground, I haven't carefully read this whole discussion. Feel free to tell me to go reread the damned thread if I'm doing so. That said... my understanding of your account of existence is something like the following:

A model is a mental construct used (among other things) to map experiences to anticipated experiences. It may do other things along the way, such as represent propositions as beliefs, but it needn't. Similarly, a model may include various hypothesized entities that represent certain consistent patterns of experience, such as this keyboard I'm typing on, my experiences of which consistently correlate with my experiences of text appearing on my monitor, responses to my text later appearing on my monitor, etc.

On your account, all it means to say "my keyboard exists" is that my experience consistently demonstrates patterns of that sort, and consequently I'm confident of the relevant predictions made by the set of models (M1) that have in the past predicted patterns of that sort, not-so-confident of relevant predictions made by the set of models (M2) that predict contradictory patterns, etc. etc. etc.

We can also say that M1 all share a common property K that allows such predictions. In common language, we are accustomed to referring to K as an "object" which "exists" (specifically, we refer to K as "my keyboard") which is as good a way of talking as any though sloppy in the way of all natural language.

We can consequently say that M1 all agree on the existence of K, though of course that may well elide over many important differences in the ways that various models in M1 instantiate K.

We can also say that M1 models are more "accurate" than M2 models with respect to those patterns of experience that led us to talk about K in the first place. That is, M1 models predict relevant experience more reliably/precisely/whatever.

And in this way we can gradually converge on a single model (MR1), which includes various objects, and which is more accurate than all the other models we're aware of. We can call MR1 "the real world," by which we mean the most accurate model.

Of course, this doesn't preclude uncovering a new model MR2 tomorrow which is even more accurate, at which point we would call MR2 "the real world". And MR2 might represent K in a completely different way, such that the real world would now, while still containing the existence of my keyboard, contain it in a completely different way. For example, MR1 might represent K as a collection of atoms, and MR2 might represent K as a set of parameters in a configuration space, and when I transition from MR1 to MR2 the real world goes from my keyboard being a collection of atoms to my keyboard being a set of parameters in a configuration space.

Similarly, it doesn't preclude our experiences starting to systematically change such that the predictions made by MR1 are no longer reliable, in which case MR stops being the most accurate model, and some other model (MR3) is the most accurate model, at which point we would call MR3 "the real world". For example, MR3 might not contain K at all, and I would suddenly "realize" that there never was a keyboard.

All of which is fine, but the difficulty arises when after identifying MR1 as the real world we make the error of reifying MRn, projecting its patterns onto some kind of presumed "reality" R to which we attribute a kind of pseudo-existence independent of all models. Then we misinterpret the accuracy of a model as referring, not to how well it predicts future experience, but to how well it corresponds to R.

Of course, none of this precludes being mistaken about the real world... that is, I might think that MR1 is the real world, when in fact I just haven't fully evaluated the predictive value of the various models I'm aware of, and if I were to perform such an evaluation I'd realize that no, actually, MR4 is the real world. And, knowing this, I might have various degrees of confidence in various models, which I can describe as "possible worlds."

And I might have preferences as to which of those worlds is real. For example, MP1 and MP2 might both be possible worlds, and I am happier in MP1 than MP2, so I prefer MP1 be the real world. Similarly, I might prefer MP1 to MP2 for various other reasons other than happiness.

Which, again, is fine, but again we can make the reification error by assigning to R various attributes which correspond, not only to the real world (that is, the most accurate model), but to the various possible worlds MRx..y. But this isn't a novel error, it's just the extension of the original error of reification of the real world onto possible worlds.

That said, talking about it gets extra-confusing now, because there's now several different mistaken ideas about reality floating around... the original "naive realist" mistake of positing R that corresponds to MR, the "multiverse" mistake of positing R that corresponds to MRx..y, etc. When I say to a naive realist that treating R as something that exists outside of a model is just an error, for example, the naive realist might misunderstand me as trying to say something about the multiverse and the relationships between things that "exist in the world" (outside of a model) and "exist in possible worlds" (outside of a model), which in fact has nothing at all to do with my point, which is that the whole idea of existence outside of a model is confused in the first place.

Have I understood your position?

If I understand both your and shiminux's comments, this might express the same thing in different terms:

  • We have experiences ("inputs".)
  • We wish to optimize these inputs according to whatever goal structure.
  • In order to do this, we need to construct models to predict how our actions effect future inputs, based on patterns in how inputs have behaved in the past.
  • Some of these models are more accurate than others. We might call accurate models "real".
  • However, the term "real" holds no special ontological value, and they might l
... (read more)
1shminux7yAs was the case once or twice before, you have explained what I meant better than I did in my earlier posts. Maybe you should teach your steelmanning skills, or make a post out of it. The reification error you describe is indeed one of the fallacies a realist is prone to. Pretty benign initially, it eventually grows cancerously into the multitude of MRs whose accuracy is undefined, either by definition (QM interpretations) or through untestable ontologies, like "everything imaginable exists". This promoting any M->R or a certain set {MP}->R seems forever meaningful if you fall for it once. The unaddressed issue is the means of actualizing a specific model (that is, making it the most accurate). After all, if all you manipulate is models, how do you affect your future experiences?

Welcome to Less Wrong! (5th thread, March 2013)

by orthonormal 5 min read1st Apr 20131761 comments

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If you've recently joined the Less Wrong community, please leave a comment here and introduce yourself. We'd love to know who you are, what you're doing, what you value, how you came to identify as a rationalist or how you found us. You can skip right to that if you like; the rest of this post consists of a few things you might find helpful. More can be found at the FAQ.

(This is the fifth incarnation of the welcome thread; once a post gets over 500 comments, it stops showing them all by default, so we make a new one. Besides, a new post is a good perennial way to encourage newcomers and lurkers to introduce themselves.)

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EXTRA FEATURES:
There's actually more than meets the eye here: look near the top of the page for the "WIKI", "DISCUSSION" and "SEQUENCES" links.
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A list of some posts that are pretty awesome

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Note from orthonormal: MBlume and other contributors wrote the original version of this welcome post, and I've edited it a fair bit. If there's anything I should add or update on this post (especially broken links), please send me a private message—I may not notice a comment on the post. Finally, once this gets past 500 comments, anyone is welcome to copy and edit this intro to start the next welcome thread.

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