28 July 1902- 17 Sept. 1994
Karl Popper died on September 17 1994. One thing that gets revived in my new book (Statistical Inference as Severe Testing, 2018, CUP) is a Popperian demarcation of science vs pseudoscience Here’s a snippet from what I call a “live exhibit” (where the reader experiments with a subject) toward the end of a chapter on Popper:
Live Exhibit. Revisiting Popper’s Demarcation of Science: Here’s an experiment: Try shifting what Popper says about theories to a related claim about inquiries to find something out. To see what I have in mind, join me in watching a skit over the lunch break:
Physicist: “If mere logical falsifiability suffices for a theory to be scientific, then, we can’t properly oust astrology from the scientific pantheon. Plenty of nutty theories have been falsified, so by definition they’re scientific. Moreover, scientists aren’t always looking to subject well corroborated theories to “grave risk” of falsification.”
Fellow traveler: “I’ve been thinking about this. On your first point, Popper confuses things by making it sound as if he’s asking: When is a theory unscientific? What he is actually asking or should be asking is: When is an inquiry into a theory, or an appraisal of claim H unscientific? We want to distinguish meritorious modes of inquiry from those that are BENT. If the test methods enable ad hoc maneuvering, sneaky face-saving devices, then the inquiry–the handling and use of data–is unscientific. Despite being logically falsifiable, theories can be rendered immune from falsification by means of cavalier methods for their testing. Adhering to a falsified theory no matter what is poor science. On the other hand, some areas have so much noise that you can’t pinpoint what’s to blame for failed predictions. This is another way that inquiries become bad science.”
She continues: Continue reading
Here are the slides from my discussion of Nancy Reid today at BFF4: The Fourth Bayesian, Fiducial, and Frequentist Workshop: May 1-3, 2017 (hosted by Harvard University)
28 July 1902 – 17 September 1994
Today is Karl Popper’s birthday. I’m linking to a reading from his Conjectures and Refutations[i] along with an undergraduate item I came across: Popper Self-Test Questions. It includes multiple choice questions, quotes to ponder, and thumbnail definitions at the end[ii].
Blog Readers who wish to send me their answers will have their papers graded (at least try the multiple choice; if you’re unsure, do the reading). [Use the comments or e-mail.]
[i] Popper reading from Conjectures and Refutations
[ii] I might note the “No-Pain philosophy” (3 part) Popper posts from this blog: parts 1, 2, and 3.
HAPPY BIRTHDAY POPPER!
Popper, K. (1962). Conjectures and Refutations: The Growth of Scientific Knowledge. New York: Basic Books.
Jump to Part (ii) 9/18/15 and (iii) 9/20/15 updates
I heard a podcast the other day in which the philosopher of science, Massimo Pigliucci, claimed that Popper’s demarcation of science fails because it permits pseudosciences like astrology to count as scientific! Now Popper requires supplementing in many ways, but we can get far more mileage out of Popper’s demarcation than Pigliucci supposes.
Pigliucci has it that, according to Popper, mere logical falsifiability suffices for a theory to be scientific, and this prevents Popper from properly ousting astrology from the scientific pantheon. Not so. In fact, Popper’s central goal is to call our attention to theories that, despite being logically falsifiable, are rendered immune from falsification by means of ad hoc maneuvering, sneaky face-saving devices, “monster-barring” or “conventionalist stratagems”. Lacking space on Twitter (where the “Philosophy Bites” podcast was linked), I’m placing some quick comments here. (For other posts on Popper, please search this blog.) Excerpts from the classic two pages in Conjectures and Refutations (1962, pp. 36-7) will serve our purpose:
It is easy to obtain confirmations, or verifications, for nearly every theory–if we look for confirmations.
Confirmations should count only if they are the result of risky predictions; that is [if the theory or claim H is false] we should have expected an event which was incompatible with the theory [or claim]….
Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability, but there are degrees of testability, some theories are more testable..
Confirming evidence should not count except when it is the result of a genuine test of the theory, and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak of such cases as ‘corroborating evidence’).
bending of starlight.
[T]he impressive thing about the 1919 tests of Einstein ‘s theory of gravity] is the risk involved in a prediction of this kind. If observation shows that the predicted effect is definitely absent, then the theory is simply refuted. The theory is incompatible with certain possible results of observation—in fact with results which everybody before Einstein would have expected. This is quite different from the situation I have previously described, [where]..it was practically impossible to describe any human behavior that might not be claimed to be a verification of these [psychological] theories.” (Popper, CR, [p. 36))
Popper lauds Einstein’s General Theory of Relativity (GTR) as sticking its neck out, bravely being ready to admit its falsity were the deflection effect not found. The truth is that even if no deflection effect had been found in the 1919 experiments it would have been blamed on the sheer difficulty in discerning so small an effect (the results that were found were quite imprecise.) This would have been entirely correct! Yet many Popperians, perhaps Popper himself, get this wrong.[i] Listen to Popperian Paul Meehl (with whom I generally agree).
The stipulation beforehand that one will be pleased about substantive theory T when the numerical results come out as forecast, but will not necessarily abandon it when they do not, seems on the face of it to be about as blatant a violation of the Popperian commandment as you could commit. For the investigator, in a way, is doing…what astrologers and Marxists and psychoanalysts allegedly do, playing heads I win, tails you lose.” (Meehl 1978, 821)
No, there is a confusion of logic. A successful result may rightly be taken as evidence for a real effect H, even though failing to find the effect need not be taken to refute the effect, or even as evidence as against H. This makes perfect sense if one keeps in mind that a test might have had little chance to detect the effect, even if it existed. The point really reflects the asymmetry of falsification and corroboration. Popperian Alan Chalmers wrote an appendix to a chapter of his book, What is this Thing Called Science? (1999)(which at first had criticized severity for this) once I made my case. [i] Continue reading
February is a good time to read or reread these pages from Popper’s Conjectures and Refutations. Below are (a) some of my newer reflections on Popper after rereading him in the graduate seminar I taught one year ago with Aris Spanos (Phil 6334), and (b) my slides on Popper and the philosophical problem of induction, first posted here. I welcome reader questions on either.
As is typical in rereading any deep philosopher, I discover (or rediscover) different morsels of clues to understanding—whether fully intended by the philosopher or a byproduct of their other insights, and a more contemporary reading. So it is with Popper. A couple of key ideas to emerge from the seminar discussion (my slides are below) are:
- Unlike the “naïve” empiricists of the day, Popper recognized that observations are not just given unproblematically, but also require an interpretation, an interest, a point of view, a problem. What came first, a hypothesis or an observation? Another hypothesis, if only at a lower level, says Popper. He draws the contrast with Wittgenstein’s “verificationism”. In typical positivist style, the verificationist sees observations as the given “atoms,” and other knowledge is built up out of truth functional operations on those atoms. However, scientific generalizations beyond the given observations cannot be so deduced, hence the traditional philosophical problem of induction isn’t solvable. One is left trying to build a formal “inductive logic” (generally deductive affairs, ironically) that is thought to capture intuitions about scientific inference (a largely degenerating program). The formal probabilists, as well as philosophical Bayesianism, may be seen as descendants of the logical positivists–instrumentalists, verificationists, operationalists (and the corresponding “isms”). So understanding Popper throws a great deal of light on current day philosophy of probability and statistics.
Phil 6334* Day #4: Mayo slides follow the comments below. (Make-up for Feb 13 snow day.) Popper reading is from Conjectures and Refutations.
As is typical in rereading any deep philosopher, I discover (or rediscover) different morsals of clues to understanding—whether fully intended by the philosopher or a byproduct of their other insights, and a more contemporary reading. So it is with Popper. A couple of key ideas to emerge from Monday’s (make-up) class and the seminar discussion (my slides are below):
- Unlike the “naïve” empiricists of the day, Popper recognized that observations are not just given unproblematically, but also require an interpretation, an interest, a point of view, a problem. What came first, a hypothesis or an observation? Another hypothesis, if only at a lower level, says Popper. He draws the contrast with Wittgenstein’s “verificationism”. In typical positivist style, the verificationist sees observations as the given “atoms,” and other knowledge is built up out of truth functional operations on those atoms. However, scientific generalizations beyond the given observations cannot be so deduced, hence the traditional philosophical problem of induction isn’t solvable. One is left trying to build a formal “inductive logic” (generally deductive affairs, ironically) that is thought to capture intuitions about scientific inference (a largely degenerating program). The formal probabilists, as well as philosophical Bayesianism, may be seen as descendants of the logical positivists–instrumentalists, verificationists, operationalists (and the corresponding “isms”). So understanding Popper throws a lot of light on current day philosophy of probability and statistics.
- The fact that observations must be interpreted opens the door to interpretations that prejudge the construal of data. With enough interpretive latitude, anything (or practically anything) that is observed can be interpreted as in sync with a general claim H. (Once you opened your eyes, you see confirmations everywhere, as with a gestalt conversion, as Popper put it.) For Popper, positive instances of a general claim H, i.e., observations that agree with or “fit” H, do not even count as evidence for H if virtually any result could be interpreted as according with H.
Note a modification of Popper here: Instead of putting the “riskiness” on H itself, it is the method of assessment or testing that bears the burden of showing that something (ideally quite a lot) has been done in order to scrutinize the way the data were interpreted (to avoid “verification bias”). The scrutiny needs to ensure that it would be difficult (rather than easy) to get an accordance between data x and H (as strong as the one obtained) if H were false (or specifiably flawed). Continue reading
|Current day Popperians, the “critical rationalists”, espouse the following epistemic principle CR:[i]
(CR) it is reasonable to adopt or believe a claim or theory P which best survives serious criticism.
|What justifies CR? To merely declare it is a reasonable epistemic principle without giving evidence that following it advances any epistemic goals is entirely unsatisfactory, and decidedly un-Popperian in spirit.
Alan Musgrave (1999), leading critical rationalist, mounts a defence of CR that he openly concedes is circular, admitting, as he does, that such circular defences could likewise be used to argue for principles he himself regards as ‘crazy’.
However, he also gives a subtle and clever argument that it’s impossible to do better, that such a circular defense is the only kind possible. So since we’re reading Popper this week (some of us), and since an analogous argument arises in defending principles of statistical inference, try your hand at this conundrum. Continue reading