… the discovery that the contexts of language are also stratified as register and genre.
and on 4/10/13:
Halliday's major specialisation has always been grammar, and one of his key discoveries (yes) was the metafunctionality of grammar in relation to field, mode and tenor.
It's not necessary to delve into the history of philosophical thought on epistemology to discount Rose's claim that theoretical constructs are "discovered" as if material phenomena; the theory of experience that has evolved in the grammar of English is instructive enough.
Semiotic phenomena — metaphenomena — such as 'stratified context' and 'metafunction', are created by being projected onto the semiotic plane by a senser sensing (ideas) or by a sayer saying (locutions). The sense in which semiotic phenomena are 'discovered' is restricted to the sensing of ideas or locutions that have already been created by a senser sensing or a sayer saying (i.e. pre-projected facts).