Positivism vs. Scientific Realism: An Example

By: Bruce
December 30, 2010

In my last post I started to discuss the differences between Positivism and Scientific Realism. To over simplify it, Positivism cares only about the predictive abilities of science and does not care about whether or not science is getting ever closer to some underlying truth. Scientific Realism takes all scientific theories seriously as approximations of an underlying truth.

Actually, despite what Deutsch says (in my last post), I feel Positivism has value. Though I generally agree with Deutsch, sometimes you just want to predict an outcome and you don’t really care about why it works. In fact, I think most people would be shocked to realize that this is how most science and engineering are done. Scientists rarely become philosophical about what their equations mean for reality.

However, Deutsch is right about one thing. Positivism ultimately fails to grasp the value of believing your explanations. It is only through believing your explanations that you can comprehend them. And only by comprehending them can you refine them into something even more useful.

Over at the Eternal Universe (a Mormon themed Physics site), I found the following post that illustrates the power and limitations of Positivism. Here Joseph Smidt, who, I promise, knows a million times more physics than I do, advocates for Positivism in at least one situation. He points out that in the famous quantum double slit experiment [1] to calculate the correct answer you have to “assume [a single] particle [goes] through both holes together.”

Double Slit

 

When you add more slits, if you want to get the right answer, you have to assume “the particle, in some sense, travels… in every path possible.”

More Slits

And finally, if there are no slits at all, then “the math we use suggests the particles take, in some sense, every possible path.”

No Slits

Joseph then asks:

Now, is this really what is going on, or is this just a model? I’m guessing it is just a model. However, it’s okay since it has significant predictive power."

Nevertheless, the question is always going to pester me: why do such bizarre models give such amazing answers?!?!

Whether Joseph realized it or not, he was advocating for Positivism over Scientific Realism – at least in this instance. And can you blame him? Are you ready to accept that a particle actually follows all possible paths from point s to point o?

But Deutsch takes this very same point and says, yes, that’s exactly what we should assume. If that is what the theory says, then that is, in some sense, a more accurate explanation of reality than any other existing alternative. If that were not so, then we’d actually have some simpler mathematical theory that gives the same results but doesn’t have to assume something as ridiculous as each particle passing through infinitely many paths simultaneously. Therefore Deutsch (taking his lead from Karl Popper) argues that our scientific theories are not primarily about prediction, but represent an actual verisimilitude of reality. [2]

I agree with both Physicists in this case, though not simultaneously. If I’m just trying to use a theory to make a prediction and I’m not prepared to try to cosmologically wrap my brain around a mind bending theory, then Positivism is probably for me. But if my goal is to explain and thus comprehend reality, then Scientific Realism is my only option. Therefore I need to take seriously the fact that a particle can be in infinitely many places at once and follow that thought to it’s logical conclusions.

Of course there is always the possibility that some future theory will replace the current one. Perhaps even one that doesn’t require me to think of particles as being in many places at once. But until that new and better explanation exists, this really is our best explanation of reality – no matter how disturbing it is.

Questions for Discussion:

Do you personally identify more with Positivism or Scientific Realism?

If a particle does take every path to get to it’s destination, what does that mean to us personally?

Notes

[1] Double Split Experiment – I’ll do a future post that explains it better, you don’t need to understand it at this point. The short version is that in quantum physics if you send a single ‘particle’ of light through two slits, it somehow goes through both of them simultaneously and then interferes with itself on the other side. Impossible? Guess again.

[2] Again we see that Popper is the father of both points of view: both Positivism and Scientific Realism. But keep in mind that Popper himself claims he is not a Positivist.

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15 Responses to Positivism vs. Scientific Realism: An Example

  1. FireTag on December 30, 2010 at 9:27 PM

    Hmmm. I was thinking about doing a post on “sum of all paths” in relation to something else, so it’s interesting to see the topic raised here, too.

    Feynmann is really the genius who is first credited with this interpretation of quantum mechanics, but the notion that ALL possibilities interfere with each other to produce reality shows up even in questions like why there are three large dimensions of space.

    The most counterintuitive thing is that it’s often the most bizarre “pathways” that dominate the outcome calculations. The philosophical implications of that are kind of boggling.

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  2. Henry on December 31, 2010 at 5:36 AM

    Bruce:
    Are people really interested in this brainy stuff? If you notice past posts, brainy posts get little to no comments.

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  3. Andrew S on December 31, 2010 at 6:38 AM

    some people are interested in this stuff, but don’t really have a lot to add.

    I guess this is why we should use “RAEBNC”

    Read and enjoyed, but no comment.

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  4. jmb275 on December 31, 2010 at 9:12 AM

    Bruce-
    I’ve liked a lot of the stuff you’ve written, and find it generally quite fascinating. I haven’t yet commented as I wasn’t quite sure what to say.

    I think you nailed it when you said that scientists and engineers don’t think much about this stuff. Truth be told, it’s the philosophers of the world (who don’t know much science) who draw conclusions about the nature of science. Scientists are interested in finding the next big theory, or at least getting the next paper published. I think we care about overall progress, but in our microcosm the impacts of what we do rarely cross our mind.

    One thing I continue to harp on in the b’nacle whenever we talk about science, truth, etc. is the error in the system and how it seems to me that people do not address it. Nature is messy, VERY messy. I think most regular people look past this because science is what’s in front of their face, as opposed to engineering. I think we see the “predictive power” of science and conclude it has truth. That is, we think scientific equations actually describe nature (hint: they don’t). In reality, there is a HUGE gap between science and the technological progress we make. That gap is filled by engineers who have to deal with the reality that no scientific, or mathematical equation has EVER perfectly predicted any natural process or event.

    I think most scientists and engineers (at least the ones I’ve asked about this), recognizing this, conclude that math is invented, as opposed to discovered. You addressed this a bit in your post on perfect circles (which most certainly do not exist in the observable world).

    As for positivism or scientific realism I’m not sure. I don’t find myself drawn to one or the other exclusively. I guess like you I see both sides of the coin. As an engineer I’m most interested in practical results regardless of any cosmological implications. My suspicion is that most engineers and scientists are similar (but that’s purely speculation).

    Likewise, scientists don’t always rigidly follow the logical facts of the scientific method. They might conclude something is “true” because it has been “verified” (which is clearly not the scientific method). I wrote a series of posts at MM a while back on how, at the end of the day, the stuff we believe and take for granted always boils down to a Bayesian inference style confidence, and that the way people differ in beliefs is really a function of their a priori distribution as well as how they form their likelihood function (what evidence is acceptable). For me, such a model takes these types of debates out of the “either/or” paradigm (you have to be positivist or a scientific realist) and places them on a vast continuum.

    Good food for thought! Thanks Bruce.

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  5. Bruce on December 31, 2010 at 10:32 AM

    Yeah, I know my posts are a bit hard to respond to. I do my best on the ‘questions’ part, but this isn’t stuff that is generally going to start a raging debate.

    I, myself, is far more the scientific realist than the positivist. (I’ll explain why in a future post.)

    I write this stuff because I need to and want to. I am hoping to find an audience, but that is okay if I don’t. Hawk can always kick me off if she wants and I’ll finish my thoughts elsewhere. ;)

    I really appreciate the feedback from the scientists in the group. You force me to keep reading other papers and other view points.

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  6. Bruce on December 31, 2010 at 10:37 AM

    jmb275,

    I recently read (listened to) Kuhn. He makes a huge point that scientific equations do not actually describe nature.

    I think, historically, this is obviously a fact. But I am not sure I agree with Kuhn that this implies a positivist world view.

    Kuhn was brilliant. I am more of a Popperian, but I think Popper has explanation gaps that Kuhn fills. (See upcoming posts for more.)

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  7. FireTag on December 31, 2010 at 12:23 PM

    Henry:

    Let me assure you that WordPress gives the permas access to lots of user stats in addition to comments. And we do use them to try to cater to and enlarge our audience(s).

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  8. Andrew S on December 31, 2010 at 1:31 PM

    ^if that were true, FireTag, I’d be kicked out LONG ago. :)

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  9. jmb275 on December 31, 2010 at 2:04 PM

    I think, historically, this is obviously a fact. But I am not sure I agree with Kuhn that this implies a positivist world view.

    I agree with you though I’m very uncertain about it all. Based on historical science, given that no equation has ever perfectly predicted anything, I have no reason to assume that someday we’ll stumble on one that will, and will hence be the underlying and all-encompassing “truth” we all seek. But perhaps so.

    BTW, Kuhn’s in my reading queue. What do you recommend?

    Oh, and we’re happy to have you here at W&T, so don’t feel bashful about posting what you like. As you can see I rarely post at all but try to remain involved. I definitely like your stuff albeit sometimes a bit too theoretical for my pragmatic side :-) .

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  10. Bruce on December 31, 2010 at 5:06 PM

    Hey, great post and rundown! (Probably explained my concern better then I could :) ) And thanks for pointing out the tension between between Positivism and Scientific Realism as I have never thought about this stuff in these terms.

    Also, I wasn’t aware Popper was the father of both points of view.

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  11. Joseph Smidt on December 31, 2010 at 5:07 PM

    Hey, great post and rundown! (Probably explained my concern better then I could ) And thanks for pointing out the tension between between Positivism and Scientific Realism as I have never thought about this stuff in these terms.

    Also, I wasn’t aware Popper was the father of both points of view.

    PS. The Bruce above was really me. Don’t know how that happened?

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  12. Bruce on December 31, 2010 at 5:24 PM

    I am not so sure Popper is really the father of both schools since Popper insists he’s not a Positivist. But people give him credit for it nonetheless (often to be derogatory, which makes it suspect.)

    jmb275,

    I’ve only listened to the Structure of Scientific Revolutions. But that is his masterwork. Good stuff.

    I listened to him thinking “I’m a Popperian, so I’m going to hate this guy.”

    To my delight, I agreed with basically everything he said save only his final conclusions. And I think he overreaches on inconsumerateability. (spelling?) The idea that two paradigms can’t talk to each other.

    I think the genius of Kuhn is that he points out that we only compare paradigm to paradigm. The idea that you falsify science just isn’t true unless you mean “falsify compared to some other theory.” But then (Kuhn argues) we might as well call it ‘validation’ after all.

    The mere existence of counter evidence means basically nothing to science. This is a bit shocking at first because we’re so used to thinking of science as ‘you try to falsify it.’ But historically, this just isn’t true.

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  13. [...] For those following my series over at Wheat and Tares, don’t miss out on my latest post: Positivism vs. Scientific Realism: An Example. Here is a teaser:However, Deutsch is right about one thing. Positivism ultimately fails to grasp [...]

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  14. jmb275 on January 3, 2011 at 5:41 AM

    Re Bruce-

    The mere existence of counter evidence means basically nothing to science. This is a bit shocking at first because we’re so used to thinking of science as ‘you try to falsify it.’ But historically, this just isn’t true.

    Oh most certainly. I’ve known that for quite some time. I realized that after taking a class on Bayesian inference. Validation is every bit as important in science as “falsification.”

    Anyway, great post!

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  15. [...] In my last post I discussed Scientific Realism vs. Positivism. The conclusion I drew was that, while both are useful points of view, Scientific Realism is the one you want if your desire is to comprehend reality. In this post, I’m going to discuss Deutsch’s arguments surrounding Reductionism and Holism, two points of view that Deutsch argues are also a hindrance to Scientific Realism. [...]

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