presumptio

Presumptio is a Latin term that means presumption, assumption, or supposition. In scholarly use, it denotes a proposition that is accepted as true for the sake of argument or as a starting point in reasoning, pending later proof to the contrary. The word derives from presumere, “to take beforehand,” with the noun form forming presumptio.

In logic and epistemology, a presumptio refers to a proposition assumed to be true in the absence of evidence against it. Such presumptions serve to guide reasoning and allow progress when information is incomplete, though they are open to revision if new data emerge.

In law, presumptio describes rules governing evidentiary burden and inference. There are two broad categories: presumptions of fact, which are inferences drawn from established facts and can often be rebutted by contrary evidence; and presumptions of law, which are legal rules that attach consequences to certain facts and may be either rebuttable or irrebuttable depending on the jurisdiction. Notable examples include the presumption of innocence in criminal proceedings, and presumptions related to legitimacy, death, or ownership in various civil-law contexts. The exact status and strength of a presumption—whether it is ultimately binding or can be overturned—vary by legal system.

Historically, presumptio has roots in Roman law and has influenced modern civil-law and evidentiary traditions. Beyond law, the concept also appears in philosophy and critical thinking as a provisional stance that should be tested against new evidence.