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Originally,fallibilism (fromMedieval Latin:fallibilis, "liable to error") is the philosophical principle thatpropositions can be accepted even though they cannot be conclusively proven orjustified,[1][2] or that neitherknowledge norbelief iscertain.[3] The term was coined in the late nineteenth century by the American philosopherCharles Sanders Peirce, as a response tofoundationalism. Theorists, following Austrian-British philosopherKarl Popper, may also refer to fallibilism as the notion that knowledge might turn out to be false.[4] Furthermore, fallibilism is said to imply corrigibilism, the principle that propositions are open to revision.[5] Fallibilism is often juxtaposed withinfallibilism.
According to philosopherScott F. Aikin, fallibilism cannot properly function in the absence ofinfinite regress.[6] The term, usually attributed toPyrrhonist philosopherAgrippa, is argued to be the inevitable outcome of all human inquiry, since every proposition requires justification.[7] Infinite regress, also represented within theregress argument, is closely related to theproblem of the criterion and is a constituent of theMünchhausen trilemma. Illustrious examples regarding infinite regress are thecosmological argument,turtles all the way down, and thesimulation hypothesis. Many philosophers struggle with the metaphysical implications that come along with infinite regress. For this reason, philosophers have gotten creative in their quest to circumvent it.
Somewhere along the seventeenth century, English philosopherThomas Hobbes set forth the concept of "infinite progress". With this term, Hobbes had captured the human proclivity to strive forperfection.[8] Philosophers likeGottfried Wilhelm Leibniz,Christian Wolff, andImmanuel Kant, would elaborate further on the concept. Kant even went on to speculate thatimmortal species should hypothetically be able to develop their capacities to perfection.[9]
Already in 350 B.C.E, Greek philosopherAristotle made a distinction between potential andactual infinities. Based on his discourse, it can be said that actual infinities do not exist, because they are paradoxical. Aristotle deemed it impossible for humans to keep on adding members tofinite sets indefinitely. It eventually led him to refute some ofZeno's paradoxes.[10] Other relevant examples of potential infinities includeGalileo's paradox and the paradox ofHilbert's hotel. The notion that infinite regress and infinite progress only manifest themselves potentially pertains to fallibilism. According to philosophy professor Elizabeth F. Cooke, fallibilism embraces uncertainty, and infinite regress and infinite progress are not unfortunate limitations on humancognition, but rather necessary antecedents forknowledge acquisition. They allow us to live functional and meaningful lives.[11]

In the mid-twentieth century, several important philosophers began to critique the foundations oflogical positivism. In his workThe Logic of Scientific Discovery (1934), Karl Popper, the founder of critical rationalism, argued that scientific knowledge grows from falsifying conjectures rather than anyinductive principle and that falsifiability is the criterion of a scientific proposition. The claim that all assertions are provisional and thus open to revision in light of newevidence is widely taken for granted in thenatural sciences.[12]
Furthermore, Popper defended his critical rationalism as anormative and methodological theory, that explains howobjective, and thus mind-independent, knowledge ought to work.[13] Hungarian philosopherImre Lakatos built upon the theory by rephrasing the problem of demarcation as theproblem of normative appraisal. Lakatos' and Popper's aims were alike, that is finding rules that could justify falsifications. However, Lakatos pointed out that critical rationalism only shows how theories can be falsified, but it omits how our belief in critical rationalism can itself be justified. The belief would require an inductively verified principle.[14] When Lakatos urged Popper to admit that the falsification principle cannot be justified without embracing induction, Popper did not succumb.[15] Though, even Lakatos himself had been a critical rationalist in the past, when he took it upon himself to argue against the inductivist illusion thataxioms can be justified by the truth of their consequences.[16] In summary, despite Lakatos and Popper picking one stance over the other, both have oscillated between holding a critical attitude towards rationalism as well as fallibilism.[15][17][18][19]
Fallibilism has also been employed by philosopherWillard V. O. Quine to attack, among other things, the distinction betweenanalytic and synthetic statements.[20] British philosopherSusan Haack, following Quine, has argued that the nature of fallibilism is often misunderstood, because people tend to confuse falliblepropositions with fallibleagents. She claims that logic is revisable, which means that analyticity does not exist and necessity (ora priority) does not extend to logical truths. She hereby opposes the conviction that propositions in logic are infallible, while agents can be fallible.[21] Critical rationalistHans Albert argues that it is impossible to prove any truth with certainty, not only in logic, but also in mathematics.[22]
Fallibilism should not be confused with local or globalskepticism, which is the view that some or all types of knowledge are unattainable.
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.
— Karl Popper
Fallibilism claims that legitimate epistemic justifications can lead to false beliefs, whereasacademic skepticism claims that no legitimate epistemic justifications exist (acatalepsy). Fallibilism is also different to epoché, a suspension of judgement, often accredited toPyrrhonian skepticism.
Nearly all philosophers today are fallibilists in some sense of the term.[3] Few would claim that knowledge requires absolute certainty, or deny that scientific claims are revisable, though in the 21st century some philosophers have argued for some version of infallibilist knowledge.[23][24][25] Historically, many Western philosophers fromPlato toSaint Augustine toRené Descartes have argued that some human beliefs are infallibly known.John Calvin espoused a theological fallibilism towards others' beliefs.[26][27] Plausible candidates for infallible beliefs include logical truths ("Either Jones is a Democrat or Jones is not a Democrat"), 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.[21]