Published online by Cambridge University Press: 28 November 2008
The school of generative phonology ‘discovered’ two things. First, that both morphophonemic and allophonic rules could be formulated in terms of distinctive features (most of which had phonetic correlates). This was one of the reasons why both types of rules were brought together under the common name of phonological rules. Secondly, that these rules normally seemed to be natural, in the sense that they showed phonetic plausibility (related, e.g., to substantive properties of the vocal tract). This naturalness was attested by their tendency to appear in identical or similar form in several languages. For some time, then, the typical generative phonologist endeavoured to write all morphophonemic and allophonic alternations he worked with as natural phonological rules.