"The theme is what is being talked about, the point of departure for the clause as message, and the speaker has within certain limits the option of selecting any element in the clause as thematic."

“Language... is a range of possibilities, and an open end set of options in behavior that are available to the individual in his existence as social man. The context of culture is the environment of any particular selection that is made within them... The context of culture defines the potential, the range of possibilities that are open. The actual choice among these possibilities takes place within a given context of situation.”

“the linguistic features which are typically associated with a configuration of situational features - with particular values of the field, mode and tenor.”

“embodies all use of language to express social and personal relations, including all forms of the speaker's intrusion into the speech situation and the speech act.”

“Michael Halliday at 80: A Tribute”

“We should not, perhaps, take it for granted that a description in terms of a formalised model, which has certain properties lacking in those derived from models of another kind, will necessarily be the best description for all of the very diverse purposes for which the descriptions of languages are needed. In assessing the value of a description, it is reasonable to ask whether it has proved useful for the purposes for which it was intended.”

“Traditionally, grammar has always been a grammar of written language: and it has always been a product grammar" A process/product distinction is a relevant one for linguists because it corresponds to that between our experience of speech and our experience of writing: writing exists whereas speech happens.”