CONCEPT
The Manifestation Requirement
Dummett's foundational constraint on theories of meaning: there can be no element of understanding a language that is not, in principle, manifested in the use a speaker makes of it—a requirement the fluent machine satisfies to an embarrassing degree, while exposing its own incompleteness.
The manifestation requirement is the load-bearing constraint in
Michael Dummett's philosophy of language: understanding must be displayable in behavior. Dummett arrived at it through the theory of meaning. If a complete theory of meaning is also a complete theory of understanding—if it specifies what a person knows when she knows what her words mean—then whatever the theory posits as the content of understanding must be cashable in something a competent speaker actually
does. Understanding that left no trace in use would be understanding that made no difference, and a difference that makes no difference is, for Dummett, no difference at all. He wielded the requirement as a deflationary weapon against the picture of meaning as a private inner state: the inner glow behind the eyes that supposedly constitutes 'really' understanding, over and above any behavioral evidence. If understanding is a glow, it is unteachable, unlearnable, and unknowable—and language could