unfalsifiability

Unfalsifiability is the quality of a claim, theory, or hypothesis that cannot be tested in a way that could prove it false. In the philosophy of science, it is often discussed alongside falsifiability, a criterion Karl Popper proposed for distinguishing science from non-science. A theory is considered falsifiable if there exists at least one possible observation or experiment that could show it to be incorrect.

Unfalsifiable statements are typically those that escape potential refutation by incorporating unverifiable mechanisms, adding ad hoc hypotheses, or appealing to non-empirical realities. They are commonly associated with metaphysical, religious, or ideological claims, or with certain forms of pseudoscience that shield themselves from refutation. Examples often cited include propositions that invoke miracles or paradign-defying exceptions that cannot be tested, or claims that automatically redefine terms to avoid contradiction.

Critics argue that not all scientifically useful theories are easily falsifiable at all times or in all contexts, and that falsifiability alone may not capture the full complexity of scientific progress. Popper emphasized falsifiability as a necessary condition for empirical content, but later philosophers such as Imre Lakatos and Thomas Kuhn have suggested more nuanced views. They highlight research programs, protective auxiliary hypotheses, and the role of accumulating evidence in determining a theory’s status, rather than a single binary distinction.

In practice, unfalsifiability is often used as a warning sign for claims that resist empirical testing. It remains a central, though contested, concept in discussions about the demarcation between science and non-science.