8.6 Falsification


By the end of this section you will discover:

  • What science means by falsification and why it is essential to genuine science.
  • Karl Popper’s advocacy of falsification to distinguish real science from pseudo-science.
  • Strengths and weaknesses of falsification theory.

Important to the scientific process is the concept of falsification. In the philosophy of science, a theory is falsifiable (or refutable) if it is contradicted by an observation that is logically possible, i.e., expressible in the language of the theory, and this language has a conventional empirical interpretation. Thus there must exist a state of affairs that obtains or not and can be used as scientific evidence against the theory, in particular, it must be observable with existing technologies. For example, “All swans are white” is falsifiable, because “Here is a black swan” contradicts it. To make falsifiability more intuitive, one can assume that the state of affairs is allowed by some other law than the one that is falsified. For example, Newton’s law of gravitation is also falsifiable—it is falsified by “The brick fell upwards when released”, which is a state of affairs that can be observed if some hidden force other than gravity acts on the brick. On the other hand, “All men are mortal” is not falsifiable, because, unlike a swan being black, a man being immortal is not an inter-subjective property—there is no shared procedure to systematically conclude immortality.

Karl Popper, Science, & Pseudoscience: Crash Course Philosophy #8

Or watch the video here.

Again Russel Payne explains the importance of this concept by introducing us to Karl Popper.

Karl Popper

Karl Popper was a philosopher in Vienna during the reign of Logical Positivism, but he was not himself a Positivist. Popper is best known for his contributions to the problem of induction and the demarcation problem. In both cases, his views were critical of the Logical Positivists.

What does Popper mean by “conjecture”?  What does he mean by “refutation”?


Photo of philosopher Karl Popper, taken before April 1987.
Karl Popper (1902-1994)

As you will recall, Hume argues that inductive arguments fail to provide rational support for their conclusions. His reason for taking induction to be irrational is that every inductive argument assumes that unobserved events will follow the pattern of observed events and this assumption cannot be supported either deductively or inductively. No purely deductive support can be given for this principle of induction because it is not a mere truth of logic. And any inductive argument offered in support of the inductive principle that unobserved cases will be like observed cases will be circular because it will also employ the very principle of induction it tries to support as a premise.

Popper accepted Hume’s conclusion that inductive inference is not rationally justifiable. He takes the problem of induction to have no adequate solution. But he rejects the further conclusion that science, therefore, yields no knowledge of the nature of the world. With Hume, Popper holds that no number of cases offered as confirmation of a scientific hypothesis yields knowledge of the truth of that hypothesis. But just one observation that disagrees with a hypothesis can refute that hypothesis. So while empirical inquiry cannot provide knowledge of the truth of hypotheses through induction, it can provide knowledge of the falsity of hypotheses through deduction.

In place of induction, Popper offers the method of conjecture and refutation. Scientific hypotheses are offered as bold conjectures (guesses) about the nature of the world. In testing these conjectures through empirical experiments, we cannot give positive inductive reasons for thinking that they are true. But we can give reasons for thinking they are false….

According to Popper, there is no rational methodology or logic for evaluating how scientists come up with hypotheses. They are just conjectures and no amount of evidence is capable of inductively confirming hypotheses in the sense of giving us a positive reason for thinking our hypotheses are true. Evidence in agreement with a hypothesis never provides it with inductive confirmation. If all the evidence is in agreement with a hypothesis, we can say that it is “corroborated.” To say that a hypothesis is corroborated is just to say that it has survived our best attempts at refutation. But contrary evidence can decisively refute hypotheses.

How does Popper suggest we “demarcate” science as a unique discipline?

The demarcation problem is the problem of distinguishing science from other things, from poetry to religion to obscure metaphysics. Popper offers an alternative to the Positivist’s Verificationist theory of meaning in addressing this problem. The Positivist’s solution to the demarcation problem had the downside of denying that we can assert as true that it is wrong to torture innocent babies just for fun. Popper’s view of the matter avoids this unsavory consequence.

Popper’s method of conjecture and refutation suggests his criterion for distinguishing science from non-science. For it to be possible to refute a hypothesis requires that there be possible observations that would give us grounds for rejecting the hypothesis. We can only scientifically investigate hypotheses that take observational risks, those that are exposed to the possibility of being shown false through observation. That is, we can take a hypothesis to be scientific if and only if it is falsifiable. For a hypothesis to be falsifiable we must be able to specify possible observational conditions that would be grounds for rejecting the hypothesis as false. But this does not mean that that it will be proven false or that it can be shown to be false (either of these confusions would lead to the absurd view that a claim is only scientific if it is false). Let’s look at some examples to make this clear.

Consider the hypothesis that all crows are black. We can specify observable conditions under which we would count this as false. Namely, seeing a white crow, or a green one. Being able to specify the observational conditions under which we would reject this hypothesis doesn’t mean that it is false. Suppose the hypothesis is true. It is still a claim that takes risks in the face of observation because we know that some possible observations would refute it. So the hypothesis that all crows are black is falsifiable.

Now consider claims made by astrology. These are typically formulated in such a vague way that any eventuality could be interpreted as affirming the astrologer’s predictions. If there are no possible observations that could refute astrology, then it is not scientific. Some astrologers might make specific and concrete predictions. These might get to claim that they are being scientific in Popper’s view, but to the degree that astrologers do take risks of being refuted by observation, they have been refuted too often….

What are “auxiliary hypotheses” and why are they important to science?

Here we will describe an objection to Popper’s method of conjecture and refutation that will set the stage for introducing the views of Thomas Kuhn. According to Popper, we make progress in science by refuting false conjectures. We never have inductive grounds for holding that proposed scientific hypotheses and explanations are true, but we can narrow in on the truth by eliminating falsehoods. Our hypotheses lead us to expect certain observations. If we do not observe what we expect to observe, then we have non-inductive grounds for rejecting our hypothesis…..

When our observations don’t accord with our expectations it tells us that at least one of the assumptions or hypotheses that lead us to expect a given observation is false. It may be the hypothesis we set out to test, or it may be one of our auxiliary hypotheses. But unexpected observations don’t tell us which is false.

Here’s a nice example of auxiliary hypotheses at work in everyday reasoning. Our hypothesis is that Hare is faster than Tortoise. This hypothesis leads us to expect that Hare will win a race against Tortoise. But suppose that, contrary to our expectation, we observe Tortoise winning the race. The hypothesis that Hare is faster than Tortoise is not thereby falsified because of the presence of a number of auxiliary hypotheses. Among these auxiliary hypotheses are the following: (i) Hare did not stop in the middle of the race for a snack, (ii) Hare did not get run over while crossing the road, (iii) Hare did not get eaten by Coyote during the race, (iv) Hare did not get entangled in a philosophical discussion about the rationality of scientific methods with his friend Gopher before crossing the finish line. When Tortoise crosses the finish line first, that tells us that either Tortoise is faster than Hare, or one of these or many other auxiliary hypotheses is false. But Tortoise winning doesn’t tell us which. The unexpected observation thus fails to cleanly refute our hypothesis….

The work of Popper in requiring all scientific hypotheses to be falsifiable in theory thus sets the stage for scientific relativism.

Strengths and Weaknesses of Falsification Theory

Popper’s falsification theory has many strengths, including:

It emphasizes sound empirical testing – scientific theories should be falsifiable by potential observations that conflict with their predictions.

It avoids the problem of induction as theories are never fully “verified,” just potentially falsified.

It delineates science from non-science – a falsifiable theory is scientific while non-falsifiable claims are not.

It encourages revision and improvement of theories when anomalous evidence surfaces rather than just seeking to justify the old theories.

It aligns with much of the practice of modern science in determining what evidence would conclusively undermine a model.

On the other hand:

Falsification can lead to a bias for simple theories – simpler falsifiable theories get favored but may sacrifice predictive precision.

Underdetermination remains an issue – data often fails to unambiguously point to one theory over all others to falsify.

It is sometimes very difficult to demarcate pseudo-science theories crafted expressly to avoid current means of falsification.

The historical record suggests science does not always strictly follow falsificationist principles.

Social factors may hinder abandonment of falsified theories if they still prove useful for technological control.

So while highlighting risks of confirmation bias, falsification criteria have limits in completely characterizing complex theory-evidence relations and the social dimensions influencing scientific theory change.


Works Cited

Bandy, Dorian K. “Karl Popper.” Wikimedia Commons, 1 Apr. 1987, https://commons.wikimedia.org/wiki/File:Photo_of_Karl_Popper_(cropped).jpg.

Crash Course. “Karl Popper, Science, & Pseudoscience: Crash Course Philosophy #8.” YouTube, 28 Mar. 2016, https://youtu.be/-X8Xfl0JdTQ.


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PPSC PHI 1011: The Philosopher's Quest by Daniel G. Shaw, Ph.D. is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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