Doctrine that nothing can be known for certain; that is, there is no infallible knowledge, but there can still be knowledge. We need not have logically conclusive justifications for what we know.

This was particularly insisted on by the American pragmatist Charles Sanders Peirce (1839-1914) in his opposition to foundationalism.

Also see: relevant alternatives theory, epistemic closure


The term “fallibilism” is used in a variety of senses in contemporary epistemology. The term was coined in the late nineteenth century by the American philosopher Charles Sanders Peirce. By “fallibilism”, Peirce meant the view that “people cannot attain absolute certainty concerning questions of fact.”[3] Other theorists of knowledge have used the term differently. Thus, “fallibilism” has been used to describe the claim that:

  1. No beliefs can be conclusively justified.[4]
  2. Knowledge does not require certainty.[5]
  3. Almost no basic (that is, non-inferred) beliefs are certain or conclusively justified.[6]

Additionally, some theorists embrace global versions of fallibilism (claiming that no human beliefs have truth-guaranteeing justification), while others restrict fallibilism to particular areas of human inquiry, such as empirical science or morality.[7] The claim that all scientific claims are provisional and open to revision in the light of new evidence is widely taken for granted in the natural sciences.[8]

Unlike many forms of skepticism, fallibilism does not imply that we have no knowledge; fallibilists typically deny that knowledge requires absolute certainty. Rather, fallibilism is an admission that, because empirical knowledge can be revised by further observation, any of the things we take as empirical knowledge might turn out to be false. However, fallibilists typically accept that many beliefs can be considered certain beyond reasonable doubt and therefore acted upon, allowing us to live functional and meaningful lives.

Some fallibilists make an exception for things that are necessarily true (such as mathematical and logical truths). Others remain fallibilists about these types of truths as well. Fallibilism has been employed by Willard Van Orman Quine to attack, among other things, the distinction between analytic and synthetic statements.[9] Susan Haack, following Quine, has argued that to refrain from extending fallibilism to logical truths—due to the necessity or a prioricity of such truths—mistakes “fallibilism” as a predicate on propositions, when it is a predicate on people or agents:[10]

One needs, first, to get clear just what is meant by the claim that logic is revisable – and, equally importantly, what is not meant by it. What I mean, at any rate, is not that the truths of logic might have been otherwise than they are, but that the truths of logic might be other than we take them to be, i.e. we could be mistaken about what the truths of logic are, e.g. in supposing that the law of excluded middle is one such. So a better way to put the question, because it makes its epistemological character clearer, is this: does fallibilism extend to logic? Even this formulation, however, needs further refinement, for the nature of fallibilism is often misunderstood.

The critical rationalist Hans Albert argues that it is impossible to prove any truth with certainty, even in logic and mathematics. This argument is called the Münchhausen trilemma.

The universal form of fallibilism is known as epistemological nihilism or global skepticism.


Historically, fallibilism is most strongly associated with Charles Sanders Peirce, John Dewey, and other pragmatists, who use it in their attacks on foundationalism (the view that any system of rationally justified beliefs must rest on a set of properly basic beliefs—that is, beliefs that are accepted, and rightly accepted, directly, without any justifying belief whatsoever—but which nevertheless are rationally supported by their connections to perceptual and introspective experiences). However, fallibilist themes are already present in the views of both ancient Greek skeptics, such as Carneades, and modern skeptics, such as David Hume. Most versions of ancient and modern skepticism, excepting Pyrrhonism, depend on claims (e.g., that knowledge requires certainty, or that people cannot know that skeptical hypotheses are false) that fallibilists deny.[11]

Another proponent of fallibilism is Karl Popper, who builds his theory of knowledge, critical rationalism, on falsifiability. In The Open Society and Its Enemies, he demonstrates its value:

A particularly impressive example of this is the discovery of heavy water, and of heavy hydrogen (deuterium, first separated by Harold C. Urey in 1931). Prior to this discovery, nothing more certain and more settled could be imagined in the field of chemistry than our knowledge of water (H2O) and of the chemical elements of which it is composed. Water was even used for the ‘operational’ definition of the gramme, the unit standard of mass of the ‘absolute’ metric system; it thus formed one of the basic units of experimental physical measurements…

This historical incident is typical; and we may learn from it that we cannot foresee which parts of our scientific knowledge may come to grief one day. Thus the belief in scientific certainty and in the authority of science is just wishful thinking: science is fallible, because science is human.

But the fallibility of our knowledge — or the thesis that all knowledge is guesswork, though some consists of guesses which have been most severely tested — must not be cited in support of scepticism or relativism. From the fact that we can err, and that a criterion of truth which might save us from error does not exist, it does not follow that the choice between theories is arbitrary, or non-rational: that we cannot learn, or get nearer to the truth: that our knowledge cannot grow.

5. Fallibilism and the growth of knowledge

By ‘fallibilism’ I mean here the view, or the acceptance of the fact, that we may err, and that the quest for certainty (or even the quest for high probability) is a mistaken quest. But this does not imply that the quest for truth is mistaken. On the contrary, the idea of error implies that of truth as the standard of which we may fall short. It implies that, though we may seek for truth, and though we may even find truth (as I believe we do in very many cases), we can never be quite certain that we have found it. There is always a possibility of error; though in the case of some logical and mathematical proofs, this possibility may be considered slight.

But fallibilism need in no way give rise to any sceptical or relativist conclusions. This will become clear if we consider that all the known historical examples of human fallibility — including all the known examples of miscarriage of justice — are examples of the advance of our knowledge. Every discovery of a mistake constitutes a real advance in our knowledge. As Roger Martin du Gard says in Jean Barois, ‘it is something if we know where truth is not to be found’.

For example, although the discovery of heavy water showed that we were badly mistaken, this was not only an advance in our knowledge, but it was in its turn connected with other advances, and it produced many further advances. Thus we can learn from our mistakes.

This fundamental insight is, indeed, the basis of all epistemology and methodology; for it gives us a hint how to learn more systematically, how to advance more quickly…

— Karl Popper, The Open Society and Its Enemies, Addenda, I. Facts, Standards, and Truth: A Further Criticism of Relativism[12]


Moral fallibilism is a specific subset of the broader epistemological fallibilism outlined above. In the debate between moral subjectivism and moral objectivism, moral fallibilism holds out a third plausible stance: that objectively true moral standards may exist, but they cannot be reliably or conclusively determined by humans. This avoids the problems associated with the relativism of subjectivism by retaining the idea that morality is not a matter of mere opinion, while offering an account for the conflict between differing objective moralities. Notable proponents of such views are Isaiah Berlin (value pluralism) and Bernard Williams (perspectivism).


Nearly all philosophers today are fallibilists in some sense of the term.[13] Few would claim that knowledge requires absolute certainty, or deny that scientific claims are revisable (though some philosophers recently argue for some version of infallibilist knowledge[14]). But many philosophers would challenge “global” forms of fallibilism, such as the claim that no beliefs are conclusively justified. Historically, many Western philosophers from Plato to Augustine to René Descartes have argued that some human beliefs are infallibly known. Plausible candidates for infallible beliefs include beliefs about logical truths (“Either Jones is a Democrat or Jones is not a Democrat”), beliefs about immediate appearances (“It seems that I see a patch of blue”), and incorrigible beliefs (i.e., beliefs that are true in virtue of being believed, such as Descartes’ “I think, therefore I am”). Many others, however, have taken even these types of beliefs to be fallible.

3 thoughts on “Fallibilism

  1. Olene Raup says:

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