Editing Logical positivism (section)

====Revisions to the criterion====

Logical positivists in the Vienna Circle recognised quickly that the verifiability criterion was too restrictive.<ref name=sep-hempel/> Specifically, [[universal generalization|universal statement]]s were noted to be empirically unverifiable, rendering vital domains of science and [[reason]], such as [[hypothesis|scientific hypothesis]], ''cognitively meaningless'' under verificationism. This would pose significant problems for the logical positivist program, absent revisions to its criterion of meaning.<ref>{{cite encyclopedia |author=John Vicker |editor=Edward N. Zalta |year=2011 |title=The problem of induction |encyclopedia=The Stanford Encyclopedia of Philosophy |edition=Fall 2011 |url=https://plato.stanford.edu/archives/fall2011/entries/induction-problem/#VerCon |quote=This initial formulation of the criterion was soon seen to be too strong; it counted as meaningless not only metaphysical statements but also statements that are clearly empirically meaningful, such as that all copper conducts electricity and, indeed, any [[universal generalization|universally quantified statement]] of infinite scope, as well as statements that were at the time beyond the reach of experience for technical, and not conceptual, reasons, such as that there are mountains on the back side of the moon. |access-date=24 August 2012}}</ref>

In his 1936 and 1937 papers, ''Testability and Meaning'', [[Rudolf Carnap|Carnap]] proposed ''confirmation'' in place of verification, determining that, though universal laws cannot be verified, they can be confirmed.<ref name=Sarkar2005/> Carnap employed abundant logical and mathematical tools to research an [[inductive reasoning|inductive logic]] that would account for probability according to ''degrees of confirmation''. However, he was never able to formulate a model. In Carnap's inductive logic, a universal law's degree of confirmation was always zero.<ref name=IEP-Carnap>{{cite encyclopedia |last=Murzi |first=Mauro |url=https://www.iep.utm.edu/carnap |title=Rudolf Carnap (1891–1970) |encyclopedia=Internet Encyclopedia of Philosophy |year=2001}}</ref> The formulation of what eventually came to be called the "criterion of cognitive significance", stemming from this research, took three decades (Hempel 1950, Carnap 1956, Carnap 1961).<ref name=Sarkar2005/> [[Carl Hempel]], who became a prominent critic of the logical positivist movement, elucidated the [[paradox of the ravens|paradox of confirmation]].<ref>{{cite encyclopedia |last=Crupi |first=Vincenzo |title=Confirmation |year=2021 |url=https://plato.stanford.edu/archives/spr2021/entries/confirmation/ |encyclopedia=The Stanford Encyclopedia of Philosophy |editor-last=Zalta |editor-first=Edward N. |access-date=2023-07-10 |edition=Spring 2021}}</ref>

In his 1936 book, ''Language, Truth and Logic'', [[A. J. Ayer]] distinguished ''strong'' and ''weak'' verification. He stipulated that, "A proposition is said to be verifiable, in the strong sense of the term, if, and only if, its truth could be conclusively established by experience", but is verifiable in the weak sense "if it is possible for experience to render it probable". He would add that, "no proposition, other than a [[Tautology (logic)|tautology]], can possibly be anything more than a probable [[hypothesis]]". Thus, he would conclude that all are open to weak verification.<ref>{{harvnb|Ayer|1936}} pp. 50–51</ref>