Saturday, April 18, 2009

Kuhn, Popper, Mars, and Venus

As my student readers already know, I recently read a large stack of student papers about scientific philosophy, in which students were responding to essays by Kuhn, Popper, Masterman, and Bacon, authors who are not only tackling some tough questions but who are arguing with each other about them.

I was pleased that many students seemed to have understood many of the key points -- these writers aren't easy to understand. Even Popper, the clearest of them, has some tricky elements. It often takes students half a quarter to get this stuff, so I'm happy that so many have gotten the broad strokes so soon.


However, not surprisingly, some students had trouble understanding the readings. I bring this up not to embarrass them (it's difficult material, and I expect to be working with the class on understanding it for a while longer), but because I was struck by how differently men and women handled readings that were tough to understand:
  • In general, men who didn't understand the readings tended to be dismissive of them, saying things like, "Maybe it's just me, but anything that's this difficult to understand probably isn't worth understanding." Or they'd talk for a page or so about how pointless the whole exchange was.
  • Meanwhile, most of the women who had trouble understanding the readings tended to focus on the character of the debate, rather than the content of it. Their papers were about moods and tone and attitude, rather than about philosophy. As a result, I read pages and pages about how Kuhn and Popper didn't get along and couldn't play nice with each other.
I don't generally look for gender differences, but every once in a while the pattern is so pronounced, so demonstrable, that it hits me with the force of a full-hand slap. This one was interesting, in part, because the class in question is a 1SC class -- a science-writing class. If this were a regular English class, most of the women would be in the humanities, and most of the men in the sciences (that's how they usually are grouped, at any rate), so I wouldn't necessarily think it was a gender difference. In a regular English class, I might chalk it up to a disciplinary difference. Also, one might hypothesize that women in traditionally male-dominated fields like engineering and computer science might react and write more like men, either because they've learned to do so in adapting to the testosterone-laden environment, or because women who think more like men are more likely at this point to be interested in those fields, or for any number of other reasons. Well, that hypothesis -- and the disciplinary hypothesis -- have been, for me, falsified. Faced with difficult readings, men and women just seem to react differently. I have no idea what to make of all of this, but I do find it interesting.


I'd like to spend the rest of this post erasing those gender differences a little, by trying to explain some of what's going on in the readings, and addressing some of the common misunderstandings.

Getting most new readers to the point where they understand this stuff requires multiple steps, and this blog entry is just the latest. Here's a recap of the previous steps:
  1. Before the readings, I introduced the subject matter and some key terms that come up in the readings (falsification, gestalt, paradigm).
  2. The second step was the reading itself. Some people get it as soon as they read it, though they're rare. Truth be told, I didn't "get" it fully the first time, so I'm sympathetic to others who don't. (Specifically, I had a knee-jerk dislike for Kuhn, and favored Popper at first. It took me a while to realize that Kuhn had something useful to say.)
  3. The third step was the first class discussion on the subject.
  4. The fourth step was an in-class writing assignment. How was this a step toward understanding? It's a phenomenon called writing to learn. The basic idea here is that many people who think they don't understand the readings will start to understand them as they write about them -- as they explain the points, they start to comprehend them better. You've probably felt this before: On page 5 of a paper, you suddenly get something you didn't get when you were on page 1. That's what I'm talking about.
  5. The fifth step was a group paper, which attempted to capitalize on something called collaborative learning. This draws on the ancient observation that people learn more by trying to explain things to other people. If you've ever noticed that you learn more when teaching someone than when trying to learn the same thing yourself, that's the basic idea here. My hope was that as students worked with each other on the paper and tried to make sense of things, they'd try explaining their ideas to each other, and things would start to make more sense as they did so.
  6. The sixth step is feedback on the previous two steps, through comments on the papers.
  7. This is the seventh step, which is basically an attempt to address some of the common questions and errors I've seen.

Let's boil down the Kuhn-Popper debate as simply as we can. The debate centers on two apparently simple questions, both of which turn out to be quite tough:

1. How do we know if something is scientific? What the heck is the difference between science and non-science? Most people agree that astrology isn't scientific, but why isn't it?

2. What constitutes good scientific behavior? What should good scientists do?

Kuhn's answer is tricky, but Masterman explains it pretty well in the second half of her article, and Kuhn, in his last article, says she's right. So let's start with Kuhn's answer, as argued by Kuhn and explained by Masterman. (Yes, Masterman agrees with Kuhn. Those of you who said she disagrees with him mistook criticism of his wording for criticism of his ideas. She likes the ideas, but thinks he writes unclearly.)

Kuhn's and Masterman's answer, in a nutshell

Imagine this: A group of people invents a model for how the world works -- a picture, a graph, a diagram, an analogy. For instance, physicists like to explain gravity by describing spacetime as a rubber sheet; if you put objects on the rubber sheet, it warps, in much the same way that planets and stars warp spacetime. Climatologists and computer scientists, meanwhile, have designed elaborate computer models of our global climate system, and when they want to understand how climate works, they rely on those models.

Those models are darned useful. But it's important to remember one thing: The model isn't the universe. It's just a metaphor for the universe. If it's a decent metaphor, it'll help us think about the universe in mostly accurate ways, but it won't be a perfect fit. Most importantly, it won't be complete. The computer simulation of our climate will be missing a variable. The rubber sheet analogy is missing some spatial dimensions.

So what do our people do, after coming up with their model/metaphor, with its holes and occasional inaccuracies?

Answer: They try to fix it. They try to fill in the holes, tweak the metaphor to cover the inaccuracies, and so forth.

They keep doing these repairs until two things happen:

1) New discoveries and new tools, like new telescopes or better computer algorithms, make it clear that the current model/metaphor has a lot of inaccuracies or holes that still need fixing; and, at the same time, ...

2) Someone comes up with another model/metaphor that challenges the old one.

At this point, the two models have a kind of run-off contest. People start to try to stress-test them, to break them, to see which one holds up best under fire. When the new model/metaphor works better, they throw out the old one and start all over again with the surviving model.

Now, let's match up the above description with Kuhn's terms.
  • The people involved are scientists.
  • Their model/metaphor is a paradigm.
  • The practice of fixing the model/metaphor, filling in holes, is puzzle-solving. A scientific period in which scientists are mostly solving puzzles is called normal science. It's called normal because most of the time, that's what's going on.
  • The stress-testing that occurs during that run-off election between competing models is extraordinary science. (Note: Popper calls that stress-testing falsification.)
Kuhn argues that normal science (the gradual fixing of paradigms) is still science, and that it's a perfectly fine, even crucial activity. The stress-testing that occurs during the occasional revolution is also good science, but it's rare, and can't really happen all of the time.

And that brings us to his answer to the second question: What constitutes good science?

Kuhn basically says, "This is the way scientists seem to work. It seems to work just fine, so this is probably the right way to do it."

Popper, in a nutshell

Popper agrees with the description of science that Kuhn presents. He thinks that's pretty much what happens, and even, in fact, kind of figuratively smacks his forehead in a duh! gesture when he says that he'd completely missed some parts of that description before Kuhn pointed them out. About normal science, he essentially says, "Holy cow. You're right. Scientists solve puzzles most of the time. How silly of me to miss that!"

However, he thinks Kuhn is wrong to defend normal science -- the gradual fixing of models and paradigms. Sure, that's what most scientists do, he grants. But the ones who do that are not very good scientists.

According to Popper, all scientists should act, all the time, like they're in the middle of one of those revolutionary periods that Kuhn calls extraordinary science -- they should be constantly trying to falsify the models, and become increasingly suspicious of those that don't survive the tests.

Put another way, Popper looks at what scientists do when multiple, competing models are duking it out, sees how scientists prefer the ones that best survive attempts at falsification, and thinks, Wow, that's really cool! Why don't we just do that all the time?

A final note

All of the above is very simplified, of course. Like a model/metaphor, it's useful in some ways and not quite complete in others. And there's more to the debate, since Kuhn and Popper respond to each other's objections several times.

But if you understand what I wrote above, then I'd say you've understood the main, most important issues.

If the above discussion helped, would you please let me know, either in a comment after the post, in an email, or in class?



  1. After I read this post, the song "I can see Clearly Now" by Johnny Nash came to mind.

  2. Wow this totally helps. I actually get the readings now.

    TO George Wong...I know what you mean.