Metaphor has historically been portrayed as colorful language – aesthetically pleasing but without cognitive import (Hobbes, 1965; Quintillian, 1921–1933). However, in recent years, cognitive semanticists such as Lakoff & Johnson (1980), Sweetser (1990), and Turner (1991) have argued that metaphor is, in fact, a pervasive phenomenon in everyday language and, moreover, that it represents the output of a cognitive process by which we understandone domain in terms of another. Cognitive linguists define metaphor as reference to one domain (known as the target, theme, or base domain) with vocabulary more commonly associated with another domain (known as the source phoros, or vehicle). On this construal, metaphoric language is the manifestation of conceptual structure organized by a cross-domain mapping: a systematic set of correspondences between the source and target that result from mapping frames or cognitive models across domains.

On this view, known as conceptual metaphor theory, a speaker invokes a metaphor whenever she refers to one domain, such as verbal argumentation, with vocabulary from another domain, such as physical combat. Conceptual metaphor theory is motivated by the existence of linguistic data like the following (from Lakoff Johnson, 1980: 4), in which argument is discussed in terms that might just as well be applied to war:

ARGUMENT IS WAR