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Falsifiability and Junk Science

Updated on October 5, 2014

Falsifiability and Meaning

Can a proposition be meaningful (true or false) if there is no known way of falsifying it?

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Philosopher of Science Karl Popper.
Philosopher of Science Karl Popper.


We start by disambiguating the term "falsifiability." Clearly, it should not be confused with "falsification" but this is a common tendency. Whereas falsification points to determining or establishing a proposition to be false, falsifiability has a different meaning as evident from the grammatically indicated distinction between the "-ation" and "-ability" endings. ("Falsification" may also be ambiguous, seldom noticed, as to whether the claim is proven to be actually false, false in some context, or necessarily false for some relevant sense of "necessarily.") Karl Popper is the author of the claim that non-falsifiable claims fail a fundamental test for being admitted into scientific status. Obviously, Popper cannot mean "falsified" because then only claims proven, or provable, to be false in some sense would be admissible as scientific! A difficulty with discerning the notion connoted by "falsifiability" may be due to this: it is surprising that there are indeed claims that cannot be falsified in the appropriate way. Actually, the meaning of "falsifiable" has to do more with evading falsification rather than with an absolute impossibility to falsify. Indeed, only analytically true statements (like "a triangle has three angles" or "it is raining or it is not raining") are not falsifiable in the absolute sense: this applies for statements that are logically necessarily true (given the definitions of the words in them) and, for other species of necessity, it applies to statements that are necessarily true in some relevant sense. For instance, in Newtonian physics the proposition made by the sentence "space is infinite" is put down as physically-necessarily true (or, perhaps, as theoretically-necessarily true) and, as such, is not falsifiable. But this is not what we mean by "falsifiable" and "not-falsifiable." So, there is some subtlety in all this - which might explain why students have difficulty grasping this very important notion.

The relevant notion of "falsifiable" can be understood as follows. Take proposition p which is a contingent proposition (it may be true and it may be false, although not both within the same context.) Now, there is an infinity of propositions, {p1, p2, ...}, not including p. This is the set of all propositions exclusive p: PROP - {p}. A falsifier pi is a proposition from PROP - {p}, such that: if pi is true, then p has to be false; or pi and p cannot possibly be true together. (Ambiguity: are we saying, "necessarily, if pi then not-p" or are we saying, "if pi, then necessarily not-p"? We take the second.) Of course, p may have more than falsifiers. It does not have to have an infinite number of falsifiers - this is the degenerate case in which p is itself necessarily false. It is sufficient for our purposes that p has one falsifier. Then, of course, every proposition that is logically equivalent to the falsifier or necessarily implies it, is also a falsifier of p. Can there be propositions that have no falsifier whatsoever? There is a view that such a proposition would itself be meaningless - so, on the classical view, it could not be evaluated itself as either true or false. The problem we are examining has to do with the claimed ongoing availability of auxiliary claims (added to p), which are said to cancel falsifiable. For instance, if it is claimed that pj is a falsifier of p, the proponent of p retorts that there is a proposition pi, such that: given pi, pj is not a falsifier of p. And this continues on and on - so that any suggested falsifier is said to fail.

The stronger view is that non-falsifiable claims, in the sense indicated above, are not meaningful. This view is underpinned by the theory that takes truth to be a matter of specified, in-principle available procedures for verification of the truth-value (true/false) of the proposition. Take as an example the old and fascinating puzzle about the inverted spectrum. If two subjects A and B experience in the first person colors in such a way that A's color-experiences always match B's color-experiences which are at the other end of the spectrum of colors - then there would be no available way for them to ascertain that their experiences differ. Some students of this problem suspect that it is not a genuine problem at all since, it is admitted, there is no available verification method. This critique does not sound intuitively correct but, again, the intuitive view about colors themselves is that they are attributes of the things of our experience itself - yet, the waves science speaks of are not colored of course. This suggests that intuition may not be a reliable ally in discussing philosophic issues.

The weaker view admits non-falsifiable claims as meaningful - if there is no other reason (based on abuse of language) for excluding them from the set of meaningful propositions; but non-falsifiable propositions cannot serve as hypotheses ever under the auspices of our modern scientific method. The exclusion of the hypothesis of intelligent design, for instance, is ont eh grounds that, unlike the evolutionary hypothesis, the design hypothesis fails tests mandated by the logic of the scientific method - one of which tests is the falsifiability test as we will see. It is remarkable that many hypotheses that are standardly showcased as "junk-science" claims may be slipping from failing other tests (when closely examined) but they are caught as soon as the falsifiability test is applied. This is not well known and there is a Supreme Court discussion in which a Justice was embarrassed not to know about this criterion.


Karl Popper on Non-Falsifiability

Karl Popper's lecture is included in standard editions of his Conjectures and Refutations.

Since 1949, Popper had turned his attention to questions like "Is there a criterion for the scientific character or status of a theory?" The problem is not when a theory may be "true" but establishing defensible criteria for drawing the distinction between science and pseudo-science given that it is possible, after all, that "science often errs, and that pseudo-science may happen to stumble on the truth."

It is not sufficient to appeal to the empiricist credentials of an investigation. What is to be accepted as a successful refutation of a scientific theory depends on logical criteria both about what counts as refuation and about what should be accepted as refutation of a claim that purports to be scientific. We can see that any consistent theory may be savageable if auxiliary hypotheses are added. It is also remarkable that many observations can continue to confirm a theory but even one admittedly disconfirming observation suffices to refute the theory - unless of course ancillary claims are added. The key seems to be blocking maneuvers that can continue, indefinitely, to defer refutation by cancelling any suggested falsifier through adding more assumption. The most fertile area of claims in which this seems to happen again and again is the domains of astrology, primitive tribal claims and in the theology of monotheistic religions but Popper told his audience that he saw the problem by reflecting on two schools of thought, widely influential in the early 20th century, which claimed for themselves scientific status: Karl Marx's theory of historico-economic development and Sigmund Freud's psychoanalysis. On the other hand, as Popper realized, so wild a theory as Einstein's Theory of Relativity, whose metaphysical projection is far more quaint than many a science fiction story, was quite controversial back then but, as it turns out, it has impeccable scientific credentials. As Popper put it, "we all - the small circle of students to which I belonged - were thrilled with the result of Eddington's eclipse observations which in 1919 brought the first important confirmation of Einstein's theory of gravitation." Notice that confirmation-tests are not sufficient to rule out the theories - Marx's and Freud's theories - which Popper suspected for being deeply unscientific. The problem then became, "Why are they so different from physical theories, from Newton's theory, and especially from the theory of relativity?"

At that time, Popper was himself sceptical about the scientific status of relativistic physics. Moreover, he was not disposed in principle against either theories of history or psychological models because, unlike physics, such approaches did not have the option of mathematizing their inquiries - in other words, Popper was not concerned with truth claims at the deepest level but, more narrowly, with the logical structure of the scientific method. Popper could not shake off the impression that those theories - Marx's and Freud's - belonged in the universe of primitive myths and creative explanations rather than in the domain of science. A hunch is not good enough, though, and, as yet. Popper did not have the insight that later dawned on him and made it possible for him to put the finger on how those sciences flunk the science test.

And, now, slowly, we come to the revealing insight that clicked to disclose the problem with those theories. Popper noticed that the advocates of Marx's and Freud's theories, acting like religious converts more or less, saw everywhere confirming instances of their favorite theories' hypotheses. It is not simply that they marveled at the explanatory prowess of their theories - which appeared impressive indeed - but that they acted as if their eyes had been opened once and for all: nothing would falsify their theories. Of course, if, as they thought, their theories had hit the bull's eye, nothing could possibly change that. Nevertheless, Popper noticed that the adherents of the theories were quick - always quick and all too quick - with explaining away anything that challenged, or falsified, their favorite theories. Those who did not believe in the theories were denounced as suffering from false consciousness (victims of their class prejudices, which prevented them from grasping Marx's analysis and acting in a way that showed that their eyes had opened to how history works); or from repression of their drives (so that their reaction to Freud's insights was itself a defense mechanism still recruited in their psychic economy insofar as they had not yet been analyzed.)

In Popper's words, "the most characteristic element in this situation seemed to me the incessant stream of confirmations, of observations which "verified" the theories in question; and this point was constantly emphasized by their adherents. A Marxist could not open a newspaper without finding on every page confirming evidence for his interpretation of history; not only in the news, but also in its presentation-which revealed the class bias of the paper-and especially of course in what the paper did not say. The Freudian analysts emphasized that their theories were constantly verified by their 'clinical observations.'.."

The turning point came in 1919 when a psychologist (operating with a version of the psychoanalytic theory), Alfred Adler, told Freud that he had a diagnosis of a child he had never met or interviewed. When Freud, stunned, asked how this was possible, Adler replied that his thousand-fold experience allowed him to reach a diagnosis without checking the patient. Freud thought that Adler might have been doing all along - all the way to his "thousand-fold" stock of prior diagnoses. This conjecture was consistent with what Popper had noticed - that the advocates of the theory would see confirmations of their theory everywhere and at all times! Did this mean that the theory could explain every conceivable case ever presented to it? Now, even though at first sight this comes across as a great achievement, notice that we are working toward unearthing something radically wrong with the logic of this type of theory. Are they really serving as explanatory hypotheses if they have confirmed already whatever conceivable or logically possible case that is presented to them? (The problem does not have to do with time, of course. It is not that the explanation is prior to the phenomenon that needs to be explained. The problem is with the broadening of the criterion: only absurd or incomprehensible cases would not confirm the hypothesis - but, of course, this means that no possible observation can falsify the hypothesis.)

Popper uses an example. Take two different cases both of which involve behaviors toward a drowning child. Person A drowns a child. Person B risks his life to save a drowning child. Freudian analysis is confirmed by both! In the case of A, the fiend is reenacting a primordial act of revenge toward a rival for maternal love (this is not the way Popper accounts for it on Freudian terms...) In the case of B, even if he has a similar phylogenetic and biographical background, he acts so differently from A because he has deflected his drives - possibly by means of the mechanism Freud called "sublimation."

Popper realized that the presumed success of the theories - that they could explain anything, including diametrically opposed actions - was actually their fatal flaw.

The case of Einstein's theory, odd as it is in its implications for how nature works, is drastically different. Einstein's theory of special relativity makes what Popper calls "risky predictions" and it is such predictions that serve as falsifiers: if not true, the theory is falsified. So, it is not that absolutely every conceivable case confirms this theory. For instance, Einstein's relativistic physics predicts that two synchronized clocks, one of which is moved very fast away from the other and then returns to its companion, will not be synchronized any more after traveling as indicated: the one that traveled in this way will be found to have slowed down relative to the other. Although there was no way to check this before the development of supersonic flight, this has always been in the theory - inherently contained in it - and serves as a falsifier: something of a red light that comes with the theory-package, so that its going on, if ever, checks the theory as being wrong. The prediction about clock de-synchronization has been now confirmed as true. This does not mean that Einstein's theory can never be rejected in the future - remember, this is not unqualifiedly about truth but about criteria for what ought to be acceptable as a scientific hypothesis. Einstein's theory was a scientific theory to begin with - in the sense that it came along with its falsifier - while Freud's theory, even thought apparently confirmed time and again - is not scientific even though it may have insights into human biophysiology and behavior, which are true.

Popper summed up the main points as follows:

(1) It is easy to obtain confirmations, or verifications, for nearly every theory-if we look for confirmations.
(2) Confirmations should count only if they are the result of risky predictions;that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory-an event which would have refuted the theory.
(3) Every "good" scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.
(4) A theory which is not refutable by any conceivable event is nonscientific. Irrefutability is not a virtue of theory (as people often think) but a vice.
(5) 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, more exposed to refutation, than others; they take, as it were, greater risks.
(6) 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 in such cases of"corroborating evidence.")
(7) Some genuinely testable theories, when found to be false, are still upheld by their admirers-for example by introducing ad hoc some auxiliary assumption, or by re-interpreting theory ad hoc in such a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from refutation only at the price of destroying, or at least lowering, its scientific status. (I later described such a rescuing operation as a "conventionalist twist" or a "conventionalist stratagem. ")
One can sum up all this by saying that the criterion of the scientific status of a theory is its falsifiability, or refutability...

Another example of how falsifiability fails in psychoanalysis is this. Let's take the case of a young boy who lives in early 20th-century Vienna and suffers from a debilitating phobia of horses which, in the given context, prevent the boy from ever leaving the house. Let us call the boy Hans - by which he is known in an actual and famous case reported by Freud. The boy was submitted to psychoanalysis by a student of Freud's. We are interested here in just a snapshot of what may transpire during the period of analysis. Let us suppose that the boy is asked the question if the horse reminds him of his father in any respect. The Freudian has essentially explained the case regardless of any confirmation or disconfirmation prospects - the horse represents a menacing figure of power, like that of a father who enjoys sexual monopoly over the boy's mother and stands between the boy and his mother; moreover, the father is able to and would remove the boy as a rival: resembling the father in the vast language of the subconscious, the "horse" triggers a castration anxiety which then gives rise to the typical symptoms of a phobia (panic, obsessive thinking, inhibitions...) The case is explained regardless of what a clinical examination of the boy may show. It is noticeable that falsifiability is bound to fail: the boy may answer the question as to whether horses remind him of his father by yes or by no. (Refusal to answer can be explained in the same way the negative answer is to be explained.) If the boy answers in the affirmative, then the psychoanalyst wins - and verifies the theory. If the boy answers negatively, or fails to answer, the analyst wins again, verifying the theory by appealing to the theory's view of how repression of drives and displacement of primal fears works. So, no matter what, the theory is verified.

In case you are wondering how Marx's economic theory of historic development is also subjecdted to criticism, here are the relevant issues. Marx studied the mechanisms of the market system with a view to showing that the tendency of profits to fall cyclically, and to rise again, is inherent to the system; moreover, the long-run trend is toward falling profit rates (recessions turning into economic depressions are to get more and more devastating each time the down-spiral of the economic cycles comes about, and, ultimately, the system will collapse and be succeeded by one that distributes the rewards only to the laborers, most of us really, who are carriers of the source of all value - which is labor.) Now, as the capitalistic system recovers from each successive downturn and keeps going, the Marxist does not, and need not, admit refutation of her theory. An auxiliary explanation or two may do: for instance, it may be said that the capitalists have now temporarily stretched the domain of exploited labor by colonizing more parts of this planet; or that artificial needs have been generated, creating ephemeral opportunities for squeezing out profit from millions of succers who drink some deadly beverage they don't really need; and so on. The problem, again, is that the falsifier is not presented - what it would take for the theory to be refuted, so we can assess its success as we can do in the case of the slowing of clocks with respect to Einstein's theory.

© 2014 Odysseus Makridis


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