Scientific Inference, part 2 of 4

March 31, 2009 at 8:06 am

Sociologists tend to divide themselves into “positivists” and “social constructionists” (with “enlightened positivist” sometimes being a middle ground), but these terms don’t do justice to the philosophy of science and if taken seriously neither model is very appealing. Likewise, many scientists will tell you that they follow Popper’s falsifiable hypothesis logic but neither does this reflect the way science is actually done (or ought to be done). We’ll go over several approaches to science, all of which agree that science is possible and desirable, but differ as to exactly what this means. The central problem that all of them are directly or indirectly attempting to grasp with is that of rigorous induction — how do we translate observations about the universe into understandings of natural law without being blinded by our preconceptions.

For both historical reasons and because he is so often invoked by practicing scientists, it’s probably worth starting with Popper. Karl Popper was originally very excited by the social theories of Marx and the psychology of Freud and Adler, at one point working in Adler’s lab. He grew frustrated though when he saw how absolutely any evidence could be made to fit within their theories with even facially disconfirming evidence being interpreted as the result of a previously unstated contingency or of the system’s ability to sublimate contradiction. In contrast, when Einstein stated his theory of general relativity he extrapolated from it a very specific prediction about how during a solar eclipse it would be apparent that the gravity of the sun bends starlight. Sir Arthur Eddington observed an eclipse and found that Einstein’s predictions were correct, but the point is not that Einstein was right but that he gave a specific prediction that could have been wrong. Popper found this contrast fascinating and set out to build an intellectual career out of contrasting science (exemplified by Einstein) with pseudo-science (exemplified by the Marxists and Freudians). Note that Popper thought that there was nothing inherently pseudo-scientific about social or behavioral inquiries, he just wasn’t fond of these particular examples.


Popper’s essential insight from this contrast was that confirmation is cheap. He gave the example of a theory that all swans are white. It would be fairly easy to make a long list of white swans in much the same way that Freud made a long list of people whose neuroses derived from sublimated sexuality. Popper said a much better thing to do would be to search for black swans and fail to find any. In fact (as seen in the photo I took at the Franklin Park Zoo in Boston) there are black swans so we can reject the “all swans are white” hypothesis. Freud never looked for his black swans, which in his case would be neurotics without sublimated sexuality. Worse yet, Freud didn’t really have a non-tautological measure of sublimation so his theory is literally not falsifiable. In contrast, Einstein made a very specific prediction about how the stars would appear during a solar eclipse such that any astronomer could examine a photo of an eclipse and see whether it matched Einstein’s prediction.

Popper can be summed up as emphasizing the importance of “falsifiable hypotheses” as the definitive characteristic of science. Such a definition worked for him as he was far less interested in how science works than in defining what is not science. This is why one of the worst things you can say about a scientist is that his work is “not even wrong” as it implies that the scientist has lapsed into metaphysics. Philosophers call this agenda “demarcation” and sociologists call it “boundary work.” In our time the principle demarcation problem is creationism whereas for Popper himself it was mostly about Marxism and psychoanalysis.

[Creationism comes in two major forms, a hardcore “young Earth” version and a more squishy “intelligent design.” Young Earth creationism argues that Genesis is literally true and about 6000 years ago God created the heavens and the Earth in 144 hours and a few generations later created a massive flood that essentially rebooted the world. Intelligent design accepts the broad outlines of the conventional scientific view of the age of the Earth and the procession of natural history but argues that divine intervention routinely adjusts natural history, chiefly through being responsible for speciation. One bizarre consequence of this is that intelligent design is too vague to test, whereas young Earth creationism gives very concrete predictions (all of which are demonstrably false). Thus in strict Popperian terms intelligent design is more pseudo-scientific than young Earth creationism as the latter gives testable (albeit false) hypotheses whereas the former does not.]

Positivists also use obviously ridiculously things like astrology, pyramidology, and parapsychology for calibrating the gun sights, with the assumption being that any good demarcation criteria should be able to explain why astrology is bullshit. Popper went so far as to say that the theory of natural selection is not scientific because in practice “fitness” is defined tautologically as “that which is associated with survival.” However in a famous lecture he eventually recanted and argued that even if it is tautological to label any given common allele as promoting fitness, we can make a falsifiable hypothesis that selective advantage is more important for explaining complex organs than such alternative descent processes as genetic drift. (Note that this comes very close to saying that while a specific hypothesis is not testable the paradigm taken as a whole is and so here Popper was implicitly embracing holism).

While the idea of the “falsifiable hypothesis” was Popper’s key contribution, it’s worth also reviewing the logical positivist school with which he was loosely affiliated. The positivists drew a very strong distinction between synthetic (empirical data) and analytic (math and logic). Any statement that could not be described as either synthetic or analytic they derided as metaphysics (or more whimsically, “music” or “poetry”). Popper’s work fit within the positivist framework as it assumed a sort of deduction-induction cycle where the scientist would use logic to derive falsifiable hypotheses from theory, then collect data to test these hypotheses. That’s the technical meaning of “positivist” in philosophy, but sociologists usually use the term casually as the opposite of “deconstructionist” or “postmodernist” to mean someone who believes that science is possible without being hopelessly mired by subjectivity. Our usage completely loses any philosophic notions about strong distinctions between analytic, synthetic, and metaphysical and many sociologists who describe themselves as “positivists” probably really mean only that they are empiricists or scientific realists.


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