Definition
In ordinary usage the term refers to a lack of clarity in a situation or in an expression. In language use it is generally regarded as an error or flaw. This view of the term was dominant until the publication of William Empson's Seven Types of Ambiguity (1930), a work that had a powerful impact on the development of New Criticism and of subsequent literary theory.
Empson used the term to describe a literary technique in which a word or phrase conveys two or more different meanings. He defined ambiguity as "any verbal nuance, however slight, which gives room for alternative reactions to the same piece of language." Included among the "seven types" is the traditional meaning of the term, but the chief interest of the book lies in examples of the ways in which ambiguity can enhance the experience of poetry.An example of Empson's analysis is his discussion of a line from Shakespeare's sonnet 73. In the poem the speaker compares his advancing age to a tree in early winter and the boughs of that tree to "Bare ruined choirs where late the sweet birds sang." The reference here is to the abandoned Catholic monasteries where choir boys once sang. Here is Empson's analysis:The comparison is sound because ruined monastery choirs are places to sing, because they involve sitting in a row, because they are made of wood, . . . because they are now abandoned by all but the grey walls coloured like the skies of winter, because the cold and narcissistic charm suggested by the choir boys suits well with Shakespeare's feeling for the object of the sonnets [the young gentleman to whom the sonnets are addressed], and for various sociological and historical reasons (the Protestant destruction of monasteries, fear of puritanism) . . . and many more relating the simile to its place in the sonnet, must all combine to give the line its beauty, and there is a sort of ambiguity in not knowing which of them to hold most clearly in mind.
Seven Types of Ambiguity represents the first sustained analysis of the phenomenon of multiple meaning, or plurisignation.