I've encountered the following claim: If we, as Popper apparantly did, view Marx and Freud's body of work as non-scientific because core tenets are not falsifiable and we apply the same rubic to Darwins theory of evolution, the latter would also appear to have non-falsifiable (core?)-tenets. According to the claim, Popper himself was well aware of that dilemma.

I don't follow the last part. Here's where I think I follow the argument:

  • Within Marx' work there's certainly things - the whole theleological attempt to predict history - that are either plain false or so wishy-washy that they're not falsifiable. Marx core axiom, the labor theory of value, is likely untestable. So I kinda follow that for Popper, Marxism is not a science.

  • Freud posits the unconscious - that we can't observe - as well as a few other concepts that can't be tested, or at least not in isolation.

What I don't understand is the claim that applying that rubic to Darwins work, we should discard it too. Darwin himself said: "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case."

To me, it appears that there is no dilemma. But maybe I'm wrong. Is my very brief summary of likely Popperian attacks on Freud and Marx grossly wrong? Did Popper ever comment on the dilemma stated at the beginning of the question, or does it simply not exist?

  • $\begingroup$ psychology is different from psychoanalysis so likely the wrong tag. Also there's no Popper tag! $\endgroup$
    – mart
    Sep 5, 2018 at 8:03
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    $\begingroup$ See Popper on Pseudo-Science : "Popper once adopted the view that natural selection is not a proper scientific theory, arguing that it comes close to only saying that “survivors survive”, which is tautological. “Darwinism is not a testable scientific theory, but a metaphysical research program” (Popper 1976, 168). In a lecture in Darwin College in 1977, Popper retracted his previous view that the theory of natural selection is tautological. He now admitted that it is a testable theory although “difficult to test” (Popper 1978, 344)." $\endgroup$ Sep 5, 2018 at 9:42
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    $\begingroup$ Popper critique of Historicism and Marxism is not so much about untestable axioms (most axioms of e.g. physical theories are difficult/impossible to test) and more about the use of ‘unconditional prophecies’ regarding the future of mankind and society. $\endgroup$ Sep 5, 2018 at 9:46
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    $\begingroup$ On Popper on Freus, see the post : Why did Karl Popper criticize Freud's theories ? $\endgroup$ Sep 5, 2018 at 9:47
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    $\begingroup$ See also Popper’s Shifting Appraisal of Evolutionary Theory. $\endgroup$ Sep 5, 2018 at 9:48

2 Answers 2


Popper's main idea about the demarcation problem : pseudo-science is untestable, is a marvel of simplicity :

On this criterion of demarcation physics, chemistry, and (non-introspective) psychology, amongst others, are sciences, psychoanalysis is a pre-science (i.e., it undoubtedly contains useful and informative truths, but until such time as psychoanalytical theories can be formulated in such a manner as to be falsifiable, they will not attain the status of scientific theories), and astrology and phrenology are pseudo-sciences.

Of course, is a philosophical (methodological) view, and its application to historical facts can be in same case difficult.

According to Popper, scientific doctrines do not emerge inductively from facts (contra Bacon and Mill); they are first imagined and then verified empirically.

Popper demarcation criteria for scientific theories demands testability.

According to Popper, theories which are testable but have been obviously refuted are scientific, for he only demands testability.

In Popper's view, metaphysics has a role : metaphysics (again contra Bacon) is sometimes important as a source of scientific inspiration.

Marxism (and, more fgenerally Historicism) is rejected by Popper as purely metaphysics (untestable) due to his claim about "unconditional" historical predictions.

According to Popper :

every event in human history is discrete, novel, quite unique, and ntologically distinct from every other historical event. For this reason, it is impossible in principle that unconditional scientific prophecies could be made in relation to human history — the idea that the successful unconditional prediction of eclipses provides us with reasonable grounds for the hope of successful unconditional prediction regarding the evolution of human history turns out to be based upon a gross misconception, and is quite false. As Popper himself concludes,

“The fact that we predict eclipses does not, therefore, provide a valid reason for expecting that we can predict revolutions.”

Regarding Darwin's theory, Popper's attitude changed.

See : Mehmet Elgin and Elliott Sober, Popper’s Shifting Appraisal of Evolutionary Theory (2017) :

Karl Popper argued in 1974 that evolutionary theory contains no testable laws and is therefore a metaphysical research program. Four years later, he said that he had changed his mind.

We may imagine that Popper's attitude changed due to his personal shift towards evolutionary approach regarding knowledge as well as due to the pressure from biology scientific community.


Scientific Method Strictly speaking the modern method of science is the Empirical Method, adopted in the late 1800s. And as you know, it requires (1) Observation, (2) Repeatability, and (3) testability/falsifiability.

Most sociological ideologies, psychological theories, etc. do not qualify as Scientific in this strictest sense. While they may not be scientific fact, they can serve as hypotheses in a useful way...with conditions. Or they may just be opinions propounded by researchers in the social sciences.

Darwinian evolution, although eventually applied to social sciences, deals with biological sciences, and has for decades been the subject of debate as to its falsifiability (and therefore, its scientific validity). It should be noted that most modern scientists have abandoned the original thesis of Darwin, and moved on to Synthetic Molecular theories to explain the Origin of Species.

If Popper became aware of the upgrade on the Evolutionary research, it may have been the basis for his change in position. It is a noble character that is willing to amend, emend, or modify his understanding of facts. Of course, any conclusion as to Popper's reasons for change must also be open to examination and falsifiability!

To respond to the OP question, Is my brief summary of likely Popperian attacks on Freud and Marx grossly wrong?, the answer is NO. Popper correctly noticed the failure of Freud and Marx to satisfy all the requirements of Scientific research; and strictly speaking, the old Darwinian evolutionary model failed too. To be consistent, Darwin had to be placed in the same camp as F & M.

But when Popper modified his understanding of only requiring "testability", he opened the door for metaphysics and hypothetical ideas to be valuable as the "inspiration" for legitimate science endeavors. (See answer above.) There is no dilemma if his particular definitions are considered. This allows the "mutation" of understanding a model when new facts are discovered.

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    $\begingroup$ As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center. $\endgroup$
    – Community Bot
    May 7, 2023 at 6:26
  • $\begingroup$ It would be helpful to have some sources/authorities for the (surprising) claims made in this answer, especially (1) equating the modern method of science with empiricism, (2) dating its adoption to the late 1800s. $\endgroup$
    – terry-s
    May 13, 2023 at 17:33

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