Wednesday, December 17, 2014

Duhem on Physical Theory and Experiment

Let's see if this works. It should come out as a slide show.
Duhem on Physical Theory and Experiment

which outlines Pierre Duhem's takedown of falsification and positivism. 

Modus tollens states that
  1. p→q
  2. not-q
  3. /.: not-p
which  is to say "p" has been "falsified." However, in this manner, heliocentrism, natural selection, and electromagnetism were "falsified." Does Popper have the grace to blush?
  1. heliocentrism→visible stellar parallax
  2. no observed stellar parallax
  3. /.: no heliocentrism
The others were similarly falsified. A new trait would be diluted before it could establish itself; permanent magnets did not have an electrical current.

But in every case, what was falsified was not the main proposition, but certain auxiliary assumptions associated with it. Heliocentrism would result in visible parallax IF the stars were close enough. Stellar distance was based on the brightness and apparent diameters of the stars; but those diameters were spurious: artifacts caused by optical aberration. The stars were really much farther away and the resulting parallax was too small to detect at the time.

Similarly, inheritance was not through the mingling of blood, as Darwin and his contemporaries thought, but through genes. That is, inheritance is digital,  not analog. A gene mutation could spread through a population until it reached a critical concentration and bearers began mating with one another. And the electron bore the electrical charge for permanent magnets.

IOW, the logical situation is:
  1. p1+p2+...+pn→q
  2. not-q
  3. /.: not-p1 OR not-p2 OR... not-pn
All of which makes the verification or falsification of scientific theories rather more complex than many suppose. The electron was a leap of faith, postulated specifically to justify electromagnetism for magnets that were not overtly electrical. Hertz and the rest kept the Maxwellian faith. So also did Kepler and Darwin maintain that the facts were wrong, not the theory!

Consider the SF possibilities.


  1. Was Heliocentrism vindicated by parallax observations?

    New blog on the kid : Duhem and TOF Spot

    I am sorry to say that I could not in this library enjoy the slide show "by Duhem" ... will see when I can!

    1. In 1803, by Fr. Giuseppe Calandrelli at the Roman College. Later by Bessel and others.

    2. My point was not to ask whether observations considered to be parallax were made, as per what you answered.

      My point was to ask whether these observations were validly classified as parallax and validly vindicated heliocentrism - and to link to my negative answer more fully given in my blog post.

  2. This sheds some light on that paper by Cartwright you linked to a while back. With the caveat that I've not finished it yet, it seems her argument is that insofar as a theory can be validated by experiment or observation, it is merely phenomenological - at best, it usefully accounts for the observations but having no claims at being true. And theories that claim to be true without any particular observations to back them up are present no compelling reasons to believe that they are in fact true - there's nothing to back them up *except* for their usefulness in phenomenological explanations. Thus, the materialist, anti-realist snake swallows its tail...

    Slide show worked perfectly for me.

  3. I used to have a physicist friend, now dead, who told this story on himself. He was attending a lecture by some famous physicist, whose name i have forgotten. Following the lecture, my friend had this conversation with the speaker:

    F: Don't you agree that theories come and go, but experimental facts remain?
    S: I take it you are an experimentalist. What experiments are you doing?
    F: I'm measuring the paths of electrons in a magnetic field.
    S: And what apparatus are you using?
    F: A Wilson cloud chamber.
    S: I see. And who told you those cloud tracks were electrons?

    There is always a theory connecting an instrumental observation with some purported underlying reality.

  4. 19/22

    Example : conspiracy theories and myths "are highly coherent, but are clearly false".

    Are the conspiracy theories for how Resurrection claim was falsely implanted in Christian Church as a collective memory really all that coherent?

    Are the conspiracy theories that are highly coherent clearly false?

    Are myths that are coherently claimed also clearly false?

    Uranus and Gaia are clearly false (as we are Christians we know that) - but are they clearly claimed?

    For instance, Hesiod claims to have heard it by word of Nine Muses, who, themselves warned him off they could tell truth - and also falsehood. Another warning off (to us more than to him) could be seen when he first observes them - the list of gods to which they sing hymns begin with Zeus of the Egide and end with Kronos of the Crooked Mind. Satan.

    Other incoherence about it being a real claim: creation of man comes very late in it. Not just six days after creation was started, but really eons. Uranus and Gaia could not have had any more human observers than Big Bang or than Abiogenesis or than Tiktaalik changing from fish to Amphibian life style.

    Ulysses returning from Troy is very coherently claimed - but why would one say it was "clearly false"?


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