supposer

Supposer is a noun meaning a person who supposes; specifically, someone who makes a supposition or assumption for the sake of argument, inquiry, or analysis. In everyday English, the term is rarely used; more common expressions include "the person who assumes" or simply "the person making a supposition."

Etymology: The word derives from the verb suppose, from Old French supposer and Latin supponere; the -er suffix makes a noun denoting a person associated with the action. In historical and philosophical writing, supposer has appeared as a technical term to denote the actor in a hypothetical scenario.

Usage: In logic, philosophy, and mathematics, the supposer may set up a thought experiment by adopting a premise and tracing the consequences. The practice is generally described using "assume" or "let" rather than the noun "supposer." When the concept is discussed, analysts often refer to the "supposition" or the "hypothetical case" rather than to the supposer themselves. Modern textbooks tend to prefer more explicit language: "Assume that…" or "Suppose that…" The term is thus mostly of historical interest or encountered in discussions about the rhetoric of argument.

See also: Suppose, Supposition, Assumption, Thought experiment, Hypothetical scenario, Logical deduction.