Popper’s falsification

The Black Swan?

Popper’s falsification approach might be a good logical exercise but that’s not how science is done. We often can’t know if a phenomenon falsifies a theory. There are way too many factors. Since I am not a philosopher, I will narrate a personal anecdote that might illuminate matters. This happened during the time I was in the beautiful city of Delft doing my research. As some would know, Delft is full of canals that are inhabited by all kinds of birds. One evening as I was walking back to my house from the TU (Delft University of Technology), I saw a black swan in one of the canals near my house. I was rather excited and pleased to have seen it. Since it was evening time, and the light was not so good, I couldn’t see it quite clearly. Anyway, long story short, as I approached nearer, much to my dismay I realized it was not a black swan but rather a poor old white swan, which had become black due to the dirty water, worsened no doubt by the litter that the boisterous undergrad students of the TU had thrown into the canal!

In Popper’s logical world, when we see a black swan, we know it’s a black swan, a falsifying piece of evidence, and that’s the end of the story: the hypothesis “all swans are white” has been efficiently falsified! But it doesn’t work like that in the real world. Of course, my anecdote is rather simple, the situation is much more complex when dealing with all kinds of noisy data that can “falsify” most theories.

Just one last thing, things would not work so simply for the falsification approach, even if we just took the above simple anecdote. Next, I will try and argue why the so-called problem of induction still stands tall and proud. Let me explain. Imagine some time after my experience in Delft, I go to Australia and see an actual black swan. However, since I have been ‘burnt’ by my earlier experience in Delft, I refuse to jump to the conclusion that it is indeed a black swan. I decide then to test if it is really a black swan or if it has been blackened due to litter and pollution. It is a simple test. I take the bird and wash it with soap. Upon washing it thoroughly, I see that it’s still black. Voila, problem solved. “All swans are white” has been falsified. But wait a minute. Not so fast. How can I know that I did a good job of washing it? Hmm. No problem, I wash it again. It is still black. Are we done? No, not really.  How can we be sure? Ok, I get down to business and keep washing the bird till late at night. By the time I am done, I have washed the swan a thousand times 🙂 And it is still black. I am really tired. Can I go home now? Can we all agree that it is a black swan, and not a white swan that has become black due to pollution? Sorry, not really: we have no idea what would have happened when I would have washed it for the 1001st time! And thus the problem of induction stands proud, entertaining no easy logical solutions!

I note that the above paragraph was simply a fun, logical exercise. It is not the central “thesis” of this post. What I really wanted to say is that practically speaking, putting it simply, science doesn’t follow the falsification approach due to the problems identified in the personal anecdote in Delft: One almost never knows if a phenomenon falsifies a theory. There are way too many factors. In the case of the blackened swan in Delft, the factor became known (pollution). But often the factors are unknown. Therefore, scientists don’t rush to discard theories based on such ‘evidence’.

So for example, consider Galileo. He couldn’t explain why objects were not flying off the surface of the earth if the earth was rotating. That was a clear piece of falsifying evidence. Let’s consider Darwin. Darwin’s data was telling him that the gradualist program of evolution was false. Data suggested that evolution was in clear and distinct stages. So the gradualist program was falsified by the data but Darwin ignored it (of course, now many agree that evolution is indeed not always a process of gradualist fine-tuning, but that’s another matter). Mendel did the same and he simply ignored a lot of the falsifying data. At a much narrower level, every experimenter knows that many experiments come out the wrong way, and therefore are reanalyzed and discarded – or sometimes just put on the shelf.

(Endnote: As for the many self-professed Popperian scientists, I refer the reader, as I did in my post on Tolstoy, to Nigel Gilbert and Michael Mulkay’s sociological study, “Putting Philosophy to Work: Karl Popper’s Influence on Scientific Practice”. It shows that scientists might say that they are following Popper, but really they are doing nothing of the sort. A further corrective would be Einstein’s words about scientists and their ‘method’: “Don’t listen to their words, fix your attention to their deeds!”)


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I am interested in understanding the links between science models and engineering models, and whether we can design a "science" for fields that require interdisciplinary research. Specifically, my field is the design of techno-social systems. Such systems are not traditional computing systems and require an inter-disciplinary approach for their design. Generally, I am interested in modeling and simulation, and seek to apply my knowledge of the same in various domains including arts, politics, science and engineering You can reach me at rrameez@gmail.com Rameez Rahman

14 thoughts on “Popper’s falsification”

  1. I think this is a clear and nice example of the problems of falsification. It seems to me your claim is simply that falsification is not possible because one can always introduce another explanation to explain away the apparent evidence of falsification (i.e. the Swan is just dirty not black). I’ve got more time for Popper – a rather unpopular position these days. You are right that one can always come up with some other explanation. However, I think one can view your example (the swan is dirty) is actually an example of a theory that can not be falsified – i.e. you describe how you can keep washing it forever. If one wanted to save Popper here one might say, your further explanation is not falsifiable. So what you’ve done is transform something that appears to be falsifiable – that the swan is white – with something that is not – it is dirty. Put simply, are no not just echoing back Poppers own position – i.e. you need to have a theory that can be falsified if you are to move forward. It seems to me what you are saying boils down to this “anything that looks like it can be falsified can actually be reformulated as a problem that can not be falsified if I substitute a non-falsifiable theory”. I think this is true but you’re doing that. Basically your theory that the swan is dirty – as you explain it – is just a poor theory because you can not test it – in the way you framed it.

    1. Hey Dave,
      About time 🙂 As I said, this was not the central thesis of the post. But let me defend this position. I would put it very briefly: With that simple example, what I was trying to say is that even the act of falsification is an act of induction (again, let me repeat: not the central thesis of the post, which was aimed more at why its not followed practically). Even the act of falsification can be subjected to the same arguments as used against induction.

      But again let me repeat, this is not the reason that falsification is not used. As I said, the “washing bit” it was a “simple, fun logical exercise”.

      1. You might be on to something here but I’m not following how falsification would have to be induction. As long as I specify what constitutes falsification for my theory, it can be falsified through direct experience without any inductive inference. For example, if my theory was that all swans are white, I could say that any black swan counts as a counterexample even if it is only black because it is dirty or I could say that only swans which can stay black after being washed in x manner y number of times count as counterexamples. It might just be a matter of being sufficiently precise about what I see as a legitimate counterexample to my theory and if I don’t provide any, then my theory is not falsifiable.

    1. Thanks for your comment 🙂 I rather wish that I had not written all that; it distracts from the main message. But still now that its there, let me try and state what I think I was trying to say back then. I guess what I was trying to say is that if we follow Popper to the letter, then even the act of falsification cannot occur. However, Popper would respond, “now you are bringing in a secondary hypothesis” (as Dave says above) etc etc, and the discussion would turn philosophical, which was not my intent at all. I was not attacking Popper from a philosophical angle but rather from a straightforward practical/historical angle. More reason why I should probably not have given this swan washing example 🙂 So I guess that’s the best I can explain it. Makes any sense?

    2. 🙂 The best that I can offer right now is that the post should be read again minus the third para (swan washing example). And/or that the gist is in the second last para, “So for example, consider Galileo…”

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