premisses

Premisses is the plural form of premiss, a term historically used in logic to refer to propositions that are assumed or stated as true and are used to support a conclusion. In modern practice, the more common singular form is premise and the standard plural is premises. The spelling premiss and its plural premisses survive in some British English contexts as an older or alternative variant, but they are far less common today.

In logical argumentation, premises function as the foundational statements from which a conclusion is inferred. An argument is evaluated for validity by its form: if the premises are true and the inferential structure is correct, the conclusion follows. Premises may be facts, axioms, or assumed propositions; their truth is not guaranteed by the argument’s logic, only the logical connection to the conclusion is guaranteed in a valid inference. Arguments can be sound (where premises are true and the deduction is valid) or unsound (where a premise is false or the reasoning is invalid).

A common source of confusion is the word premises, which also means a building or property and is unrelated to the content of an argument. The two senses share spelling but differ in meaning; context usually clarifies which sense is intended. The word premiss (and its plural premisses) is largely historical, and most modern texts avoid it in favor of premise/premises.

Etymology traces premise to Latin praemissus, meaning “sent before.” In use, premises refer either to the statements advancing an argument or, in real estate language, to the property or grounds occupied by an organization. See also inference, syllogism, and argumentation theory.