ABSTRACT
All communication relies on physical substance. Communication involving language uses a number of different kinds. Spoken language is carried by sound waves originating from the human vocal tract (or occasionally a speech synthesizer). Written language is carried by marks on a prepared surface such as paper or painted metal, by points of light on a screen, or by three-dimensional letters, such as those used in neon signs. The sign languages used by the deaf (which are as complex as any spoken language) are carried by movements and configurations of the hands. These primary substances of language can be relayed by secondary substances such as celluloid film, computer disc, electric cable, magnetic tape or radio waves. Discourse types are often associated with particular choices and combinations of substance. A ‘chat’, for example, is carried by sound waves and may be relayed by telephone, but is not printed on expensive paper or carved in stone. A ‘letter’ is typed or written on paper. A ‘tv news broadcast’ is first written, then relayed by auto-cue, then spoken, then relayed by cable or by radio waves.
