infallibilis

Infallibilis is a Latin adjective meaning not fallible or incapable of error. It is built from the negating prefix in- added to fallibilis, the latter deriving from fallere, to deceive or err. In Latin, infallibilis is used to describe things regarded as free from error, though the strictness of that claim depends on the context and era of the text.

In philosophy and epistemology, the related concept of infallibility concerns whether a belief-forming process or a method can be entirely error-proof. Infallibilist positions contend that knowledge requires certainty or justification that cannot fail, while many theories of knowledge accept fallibility as intrinsic to human cognition and still allow knowledge. Debates often contrast infallibilist and fallibilist accounts of justification, perception, memory, and scientific reasoning, emphasizing the practical and theoretical limits of claiming certainty.

In theology, infallibility is most prominently discussed in the context of the doctrine of papal infallibility in the Roman Catholic Church. Defined at the First Vatican Council in 1870, the doctrine holds that the Pope is preserved from error when pronouncing ex cathedra on matters of faith and morals. The concept has been the subject of extensive theological and historical analysis, with discussions focusing on its scope, conditions, and implications for ecclesial authority and doctrinal development.

In modern usage, infallibilis itself is primarily found in Latin texts and scholarly discussions. In everyday English, the related noun infallibility is far more common, while infallibilis appears mainly as a descriptive term in quotations, translations, or titles that engage Latin rhetoric.