Looking twice at the history of science

Wednesday, May 1, 2013

Saving the symmetry principle, IIIa: truth in the history of science

This post continues my series on the symmetry principle, with apologies to anyone who has been holding their breath since my last post five weeks ago. That was a piece of conceptual ground-clearing in which I argued that esoteric-seeming distinctions can make a big difference to the answers we give to important questions. In this post and the next I want to illustrate the point by distinguishing between different senses of the claim—which historians sometimes equate with the symmetry principle—that “people don't believe things just because they are true.” Expand post.


  1. Somehow you pick up the stick at the wrong end, I think.

    You cannot change someone's belief by showing them evidence to the contrary. I seem to remember a story how Louis Agazzis traveled to the Galapagos, in oder to see the evidence that convinced Darwin of natural selection and was not impressed.

    Likewise, I read Vanessa's post as stating that it's useless to brandish evidence to creationists and try other strategies instead.

    Er, well that might amount to something like psychotherapy or a Socratic method rather than science, but it might be more efficient in dealing with 'em.

    1. Hi Joachim, thanks for the comment. I think we read Vanessa's post in similar ways. Like you, I took her to be downplaying the role of evidence in scientific debates and playing up the importance of other factors. Also, she was suggesting that this was true for *both sides* of any debate; she was suggesting that evolutionists are just as impervious to the evidence as creationists are.

      However only the second part of this thesis (the bit after "Also") has anything to do with the symmetry principle. As I pointed out at the beginning of this post, the symmetry principle itself gives no grounds for preferring non-evidential explanations over other sorts of explanation.

      Also, I found that Vanessa's post mixed up the idea just stated--the relative importance of non-evidential factors--with a bunch of other ideas that differed significantly among themselves, and which were responsible for much of the brouhaha in the comments section of the post. Maybe this ambiguity was inevitable given the brevity of Vanessa's post. But the same conceptual confusions tend to occur quite often, in my experience, in academic discussions about how to do history of science. Hence the need for this post and the next one.

      Finally, I'm not sure what your Galapagos example is meant to show. Are you saying that since Agassiz and Darwin disagreed about the strength of the evidence at Galapagos, one of them must have been relying on something other than the evidence?

    2. It probably only shows that the path of interpretation that leads from evidence to conclusion is often so long and complex that evidence does not directly tell on the correct conclusion.

    3. I think your last comment is correct as long as you are using the term "evidence" to mean "fact" in sense II defined in the above post, ie. to mean "a statement about raw data or empirical observations."

      But in this series of posts I have been using the term "evidence" in a broader sense to mean anything that an orthodox internalist historian of science would consider as a legitimate argument for a scientific claim. This includes "facts" in sense III, but it also may include background assumptions, tacit metaphors, methodological preferences, and so on.

      So Darwin and Agassiz reached different conclusions from the "evidence" (in the narrow sense). But perhaps this difference can be explained in terms of the "evidence" (in the broader sense).

      I agree that the distinction between "internal" and "external" explanations is a fuzzy one. However this is a problem for Vanessa as much as it is for me, since the symmetry principle cannot even be stated without making a distinction of that kind.

    4. You wrote:
      "But in this series of posts I have been using the term "evidence" in a broader sense to mean anything that an orthodox internalist historian of science would consider as a legitimate argument for a scientific claim. This includes "facts" in sense III, but it also may include background assumptions, tacit metaphors, methodological preferences, and so on."

      It's all about scientific matters, I agree, they are internal to science. Hence these issues differ from political motivations and other external factors that some sociologists of science want to sniff out.

      But to include them as evidence stretches the notion too far for my taste. A ceteris paribus or an organism metaphor for, say, ecosystems is an frame that suggests to interpret the evidence in a certain way. A machine metaphor for ecosystems might suggest a different interpretation of the same data/evidence. Likewise, a preference for surveying vegetation will yield evidence different from a preference for field experiments, which in turn will yield evidence different from glass house or lab experiments. Again, this has to be considered when interpreting the evidence.

      These issues are not yet external to science, but already belong to the context of interpretation. Even if the demarcation line was fuzzy, a political motivation or loyalty to a colleague or friend would clearly be external factors.

      The problem with sticking to internal factors is that, sometimes, contrary views can be equally defended depending on the choices made for interpreting the data. What's a historian/sociologist of science to do other than stepping out of the internal context and look for external factors explaining these different choices?

  2. I have a bunch of remarks, which I'll post in separate comments.

    I think science studies is still hashing out the legacy of Kuhn's relativism, as expressed in Structure this way:

    We may, to be more precise, have to relinquish the notion explicit or implicit that changes of paradigm carry scientists and those who learn from them closer and closer to the truth.

    and later on (in his Rothschild Lecture at Harvard in 1992),

    I am not suggesting, let me emphasize, that there is a reality which science fails to get at. My point is rather that no sense can be made of the notion of reality as it has ordinarily functioned in the philosophy of science.

    Any adherent of this viewpoint will have little use for your explanations 3-5.

    I have taken these quotes from Steven Weinberg's critical essay "The Revolution That Didn't Happen". Weinberg is of course a Nobel-prize winning physicist. He reacts forcefully to this philosophy:

    All this is wormwood to scientists like myself, who think the task of science is to bring us closer and closer to objective truth.

    Another strong critic is the filmmaker Errol Morris, also as it happens a former student of Kuhn and once the target of a ashtray Kuhn hurled at him. He writes:

    For those who truly believe that truth is subjective or relative (along with everything else), ask yourself the question – is ultimate guilt or innocence of a crime a matter of opinion? ... If you were strapped into an electric chair, there would be nothing relative about it. Suppose you are innocent... would you be screaming, “I didn’t do it. Look at the evidence. I didn’t do it.” Nor would you take much comfort in the claim, “It all depends on your point of view, doesn’t it?”

    Kuhn reiterated his position in the Afterword to his Black-Body Theory and the Quantum Discontinuity, 1894-1912:

    [T]o understand scientific progress we need not suppose science moves closer and closer to the truth; the same phenomena follow from the assumption that science simply evolves from its current position under the pressure of currently available argument and observation...

    I am struck that the same Afterword contains Kuhn's most stirring defence of the notion of historical truth. To the question, why should we even care whether Planck or Einstein first proposed the quantum of energy, Kuhn responds:

    I wrote the book as an historian of ideas, and my primary object was just to get the facts straight. Different specialties differ in the facts they must get straight, and no one is obliged to engage in this one. But a person who assigns no importantce to such questions ought not even make the attempt.

    Given Kuhn's "corrosive skepticism" (Weinberg) about scientific truth, and the influence of Kuhn on modern historiography, is it any wonder that (as you put it):

    I sometimes get the impression that, in the eyes of historians and sociologists of science, anyone who uses the words “truth,” “evidence,” or “reality” when discussing past or present science must be doing something wrong.

    1. Thanks for posting these revealing quotes. I am very sympathetic to your claim that "science studies is still hashing out the legacy of Kuhn's relativism." That is, I agree that many methodological preferences among historians can be traced back to skeptical or relativist arguments advanced by Kuhn and others in the second half of the 20th century.

      It is less clear how direct this legacy is. Will Thomas and I have had a long-running conversation about this, whose latest installment can be found here:

      Will tends to emphasise the indirectness of that legacy, and to see the realist/social constructivist debate about *how science works* as a distraction from more pressing issues about *how to do history.* I tend to emphasise the directness of the legacy, and insist that the issues about how to do history--which are indeed pressing--cannot be sorted out without addressing the realist/constructivist issue.

      Will and I came to agreement in the comments section to which I just linked. If I may quote myself, I conceded that:

      "I’m persuaded that there is not much value in writing articles or blog posts attacking the philosophical claims about science that are put forward by social constructivists, in the hope that these arguments will trickle down to the practice of historians."

      The reason I bring all this up is that your comment helps me to clarify my position on this. Yes, a defense of scientific realism, or a reply to the Harry Collins' "experimental regress" argument, is unlikely to change the way people do history. But this is not because there is no link between the philosophy and the history. Rather it is because historians *do not realise* the extent to which their current historiographical preferences depend on these philosophical questions.

      Hence the need for two tasks: firstly, to reveal the extent of this dependence; secondly, to revise our historiographical preferences in a way that reduces this dependence.

      This brings me back to your remarks about Kuhn. I take you to be making two points. Firstly, Kuhn-style relativism about science is hard to defend--especially if, like Kuhn, one wants to give a "stirring defence of the notion of *historical* truth." Secondly, some current historiographical preferences depend rather heavily on Kuhn-style relativism--as you put it, "Any adherent of [Kuhn's] viewpoint will have little use for [my] explanations 3-5."

      It seems to me that the second point is the one that now needs to be emphasised. For those of us interested in the practice of history, the pressing question is not whether Kuhn was right to be a relativist. The pressing question is whether or not current historiographical preferences are dependent on endorsing Kuhn's relativism or rejecting it.

      This position (partially) renews my disagreement with Will, since now I am saying that new moves in the relativist/social constructivist debate *should* cause historians to change at least some of their methodological preferences. It is only a partial disagreement because I think that historians are not properly aware of this dependence, and also this dependence is often undesirable.

    2. Yes, you read me correctly. I belong to Weinberg's camp: I happily say things like "General Relativity is closer to the Ultimate Truth About The Universe than Newtonian mechanics, which in turn was way closer than Aristotelian physics."

      Though I have to tie that to a concession. While I have no problem with such Ultimate Truth assertions, I concede they are problematic: one assumes this philosophical stance on faith, one can't prove it.

      Kuhn tried to fashion an alternative philosophy, not very successfully (IMO). To put it bluntly, Kuhn was a superb historian but a crappy philosopher --- indeed, to anticipate my next comment, Kuhn was a crappy philosopher because he was a superb historian.

  3. "You cannot change someone's belief by showing them evidence to the contrary" seems to be a bit of an exaggeration to me. I'm sure that there must be examples of this happening. The only one I can readily offer is the conversion of Hermann Bondi to the Big Bang theory after the discovery of the cosmic microwave background. Simon Singh in "Big Bang" says that Bondi had once challenged advocates of the Big Bang Theory to "show me some fossils of it" and as Singh says, he had to accept that the CMB was a perfect fossil. Singh also says that in a poll in 1959, 33% of US astronomers believed in the Big Bang and this % rose to 69 in 1980 - the inference being that it was the CMB discovery in 1964 that changed most minds. Now of course one could postulate other factors, but surely this piece of evidence must have been a major factor, and the only factor in many cases.

    Re factual evidence, I'd prefer to state reason 5 as something like this: "I have made repeated observations and they are consistent with one another and with this theory, and less consistent with other theories; therefore I believe this theory".

    1. Thanks for your comment Jim. My reply to Joachim above may be relevant to your point about reason 5. In reason 5 I did not mean to say that appeals to factual evidence were a *complete* account of the internalist's view of how scientists decide between theories. I just meant that somewhere along the line they usually make an appeal to facts in my sense II, ie. to "raw data and empirical observations."

      The reason I included reason 5 in the list is that historians and sociologists seem deeply suspicious of anyone who claims that "facts" help to explain people's beliefs. I wanted to show that this reflex is not always justified, and that we should think about what a person means by "fact" before we jump down their throats and accuse them of misunderstanding the nature of science.

      I pretty much agree with your first paragraph. However I would add that claims like "You cannot change someone's belief by showing them evidence to the contrary" are another source of ambiguity in these debates. Here are some readings of Joachim's claim, in descending order of boldness:

      I "The evidence never has any role in changing a person's belief"

      II "The evidence is never the main reason for a change in belief"

      III "The evidence is never the only reason for a change in belief"

      IV "The evidence is never the only reason a person acquires a belief (as opposed to changing a belief)"

      I expect that Joachim would reject I. I also expect that you (Jim) would accept IV. It is just obvious that there were many non-evidential factors--such as his good state of health at the time, and his ability to read scientific papers--that were necessary conditions for Bondi's belief in the Big Bang theory. Of course Bondi's ability to read, etc., do not really explain the *change* in his belief, because his ability to read was constant across his change in belief.

      If I am right so far, then the debate is really about II and III. But that's not the end of it, since Joachim could reject both II and III but still say that it is *rare* for the evidence to be the main or the only factor in changing a person's belief. And I expect that this is what the debate is *really* about: overall, across a wide range of cases, what has been the relative weight of evidential and non-evidential factors in changing people's beliefs about nature?

      This is essentially an empirical question that calls for detailed historical study. No amount of a priori reflection on the nature of science is going to settle it.

      What I object to (to bring this back to my original post) is precisely the attempt to answer this question with a priori reflection. It seems to me that this was what Vanessa was trying to do in her post on the symmetry principle.

      I also think this is a fairly common practice in science studies. One begins with the symmetry principle, ie. the claim that historians should not argue from the truth of a person's belief to the goodness of their evidence for that belief. One then argues from this (perfectly reasonable) methodological claim to the empirical claim that the evidence has played relatively little role--or at least a much smaller role than we thought--in the beliefs of past scientists. This empirical claim may be true, but it does not follow from the symmetry principle.

  4. What sociologists of science probably claim is not that scientific evidence cannot change scientific commitments, but that a non-scientific element is always involved in such a move (as well as in resistance to change).

    I cannot give an example of a physicist, but Thomas Huxley was never convinced about natural selection as the force behind evolution (it remained a working hypothesis for him). He nevertheless joined Darwin's camp. I guess that sociologists of science would take that as a career move or politically motivated choice, while scientists quote his famous response to the idea of natural selection as evidence for the impact of evidence: "How extremely stupid not to have thought of that!"

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