Pur Autre Vie

I'm not wrong, I'm just an asshole

Saturday, December 01, 2012

Truth and Science

So I want to start out by repeating my caveat that I am very untutored in philosophy.  These posts are definitely in the "idle speculation" category.  And while people seem to want to take this in a very sophisticated direction (see the back and forth between Sarang and Tarun), I don't really have that kind of ambition.  I am worried about what seem to me to be very low-level questions.

But so anyway, in comments on my previous posts, I think Sarang takes the following position:

1.  What we mean by "truth" is a relationship of ideas/statements to the mind-independent real world (correspondence theory of truth).  If we want to talk about some other concept of truth, we should find a new word, because "truth" is taken.

2.  The real world has no necessary connection to our observational data.  (That is, you can't rule out the possibility that a demon or whatever is fooling your senses—this is what I take to be a "Cartesian demon.")

It seems to me that an implication of this view is that science has nothing to do with the truth.  So for instance, Dave engaged in some discussion of the Ptolemaic model of the solar system.  The story, maybe not quite historically accurate, is that scientists had devised a model of circular motion of planetary bodies around the earth.  However, the models had to be heavily refined with more and more circles (epicycles), lest the models give wrong predictions about where we would observe planets to be in the sky.  The models became very precise but very convoluted, and, per Dave, they would not have given you much predictive power if you were to discover a new planetary body.  The Copernican model of planetary motion (with the Sun as the center of the planets' orbit), while less accurate at predicting the movement of known planets, was much simpler and could more accurately predict the paths of new planets as they were discovered (I am hazy on this part).  If you add the concept of elliptical motion to the Copernican system, you get a pretty simple and accurate model of planetary motion, or so I am told.

Okay, so that's an interesting discussion, but I don't see how the Copernican model can have any claim on the truth, if Sarang is right.  After all, the Copernican model is merely better at explaining/predicting empirical data, and empirical data has no necessary relation to the real world (see point 2 above) and therefore no necessary relation to the truth.  For all we know, the planets actually move according to the Ptolemaic model, but God or a demon or whatever distorts our visual data and makes us think that the Copernican model has more predictive power.  The Church was right and we have been fools.

Likewise, I don't see how you could believe that, say, it is true that global warming is happening, if our observations of temperatures, polar ice caps, etc. are suspect.  Again, the theory might closely fit the data, but the data themselves don't have anything to do with the real world.  Truth is transcendental, not empirical, and humans can access it only through, I don't know, divine revelation or something.  Certainly not through science.

So while Sarang finds my viewpoint inadequate because it doesn't allow for Cartesian demons, I find his viewpoint unappealing because it divorces truth from human understanding.  We have no grounds to say that A is true while B is false.  Maybe we are compelled to accept certain things as provisionally or apparently true (so that we can build bridges, navigate ships, etc.), but this is a concession to the exigencies of life, not a commitment to empirical truth.  While scientific theories can be coherent and useful and predictively powerful, none of this can make them true.  Likewise, a theory can be incoherent or useless or contradicted by the evidence, and none of this can make it false.  Which means, by the way, that we should not care whether scientific theories are true or false, but merely whether they appear to be true or false to us.  In this, it seems to me that our current linguistic conventions do not fit Sarang's view, since we behave as though the sine qua non of a successful scientific theory is that it not be "false."  Indeed we treat observations that contradict a theory as though they have some bearing on its truth!  We would do much better to focus on a theory's apparent or empirical truth (its relationship to empirical data), though per Sarang we really need a new word for this concept, since this is not what people mean when they say a theory is true or false.


Blogger Sarang said...

"For all we know, the planets actually move according to the Ptolemaic model, but God or a demon or whatever distorts our visual data and makes us think that the Copernican model has more predictive power. The Church was right and we have been fools."

This is in fact a logical possibility and I'm not sure why you're unwilling to accept it. For most everyday purposes we _assume_ that there is no Cartesian demon / the whole world isn't just a dream, but it can't be ruled out, and it could be "true" in the ordinary-language sense of the word. (After all we have all had things happen to us in dreams; this is what I mean by there being intuitive force to the Cartesian demon argument.) If we make fairly strong assumptions about induction then we can justify (some) scientific inference. The motivation for making + acting on these assumptions is pragmatic in a Pascal's wager sense -- if induction is invalid, the future is utterly unpredictable so there can be no reasons for or against acting.

Long story short, scientific inference is a sensible procedure (i.e., typically yields "true" predictions) _assuming_ Cartesian demons don't exist and induction is generally valid. But of course this is an assumption we can't prove.

You are getting notions of "truth" and "proof" mixed up here I think. On the ordinary-language notion of truth it is possible for something to be true or false regardless of whether we have any means of establishing that it is true or false. The Cartesian demon hypothesis is _in fact_ either true or false; we have no access to which it is, so have to make assumptions about it. Scientific predictions (say, Uranus will be located at x at time t) are also either true or false; we just don't know what they'll be until we do the experiment. As for scientific _stories_ (the earth goes around the sun, etc.) I tend to think it is a category error to refer to them as "true" or "false"; they are either falsified or not falsified; I am not sure it really makes sense to call them true or false.

(One often refers to a scientific story as "true" but I think this is best understood as a shorthand for "it has a track record of yielding reliable predictions." Otherwise one runs into annoying issues like whether quantum mechanics means that Newton's theory is "untrue.")

11:35 AM  
Blogger Sarang said...

Sorry that was an excruciatingly poorly written comment but I hope the gist of it is clear. I am not sure, by the way, that believing in the possibility of a Cartesian demon automatically forces me to the correspondence theory of truth (though the converse is probably true): while I certainly believe your statement (2), I am not sure I believe all of (1). Though it's natural to posit a real world Out There, I am not sure it is necessary to interpret scientific predictions or other inductive statements.

Do you agree that there is a distinction between scientific stories like "the moon goes around the earth" and predictions like "a large blob of white can be seen through the telescope at such-and-such points in the sky"? I know there are some sophisticated arguments that deny a sharp distinction here but I would claim that these are very different sorts of statements.

12:09 PM  
Blogger James said...

So, Putnam (in the '80s) would say something like this:

If a Cartesian demon were at work, we could not successfully refer to that Cartesian demon, and therefore a sentence like, "There is a Cartesian demon at work!" could never be true.

I am not ready to adopt that line of argument, but I guess I believe something like this: There is no point giving something the label "truth" if it has no possible interaction with human minds. If neutrinos were truly undetectable and truly had no mass or whatever, there would be no reason to study them (and of course no possibility of doing so). When we talk about the truth, we are (or ought to be) talking about the world we live in, and not some other world about which we can only speculate.

Now it is another story if the Cartesian demon could be found out, or if the brains could escape the vat. In that case the demons and the vats would be in the same world as the minds, even if this weren't readily apparent. Then theories about demons and vats would be susceptible to truth or falsity. But if we are talking about things that are and will forever be remote from our minds, then I think it is not useful to bicker about truth and falsity. One scientist says that the world includes electrons because God lost a game of checkers to the Devil; another says that electrons came about when a mystical turtle got angry at a deceptive wine merchant. In what sense can these sorts of claims be true or false? (I suppose you might respond, "In the ordinary sense.")

As for scientific theories generally, I don't think they can be true in some transcendental way, but my conception of truth allows for things to be "true enough" or "true within a particular context." So it may not be true in some deep sense that the moon orbits the Earth, but for the purposes of the Apollo engineers it was "true enough" or "true within the required parameters" or something.

I do think there is a distinction between a high-level model and low-level sense data, but I don't think it is hugely important. (For one thing, even our "raw" sense data is highly processed, for lack of a better word, by the time it gets to our consciousness. The visual field is not a straightforward mapping from retinal interactions.) Sense data is usually easier to accept or reject than high-level models, and when a society determines what to include in its collective empirical world, it is generally willing to override dissent fairly quickly when it comes to simple observations. (But see the unreliability of eyewitnesses.) High-level theories are harder and less prone to forced consensus, in part because they are about competing notions of the best way to view the world. That is, they are value-laden.

Anyway I suppose I might be missing your point, but this is what I think. I suppose you might say that I am simply trying to bifurcate truth into "transcendental truth" and "empirical truth," and then claim the term "truth" exclusively for the latter. I think that is roughly what I am doing. But I do think there is something non-obvious about the idea of an "empirical world" that is built by our minds rather than simply impinging on them.

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