Supposition

Supposition is the act of assuming something for the sake of argument or as a premise, or the thing that is supposed. In everyday language, a supposition is a belief or conjecture that is not proven, used to explore consequences or to reason about a scenario. It is closely related to but often less committed than a hypothesis.

In formal contexts, supposition is distinguished from hypothesis and from presumption. A supposition may be adopted without evidence and may be used as a working premise in reasoning. A hypothesis, by contrast, is typically a testable proposition proposed for investigation. A presumption is an assumption taken to be true with a higher degree of likelihood or authority, while an assumption is any premise accepted for the sake of argument.

Etymology traces supposition to Latin suppositio, from supponere, meaning to place under or to substitute. In English usage, common phrases include “under the supposition that” and “for supposition’s sake.” In philosophy of language and logic, supposition also denotes a technical notion related to how terms stand for objects or propositions within different uses of language, contributing to analyses of reference and meaning.

Examples: “Let us suppose that it rains tomorrow.” “Under the supposition that all rules are followed, the experiment should yield valid results.” While the term is versatile, it generally conveys provisional acceptance rather than proven fact.