If meaning is to be mentioned in linguistics at all, it should be defined as resulting from the necessity, for the speaker, of choosing at a point among several units for the expression of some element of the experience. Choice, on that level, implies meaning, and meaning is there only if there has been a choice. Syntactic functions, such as the ones expressed by prepositions or cases, are, in a way, predetermined: a dative relation is expected after a verb meaning ‘to give’. But the choice often exists between the presence of the dative complement and its absence: 'advice' can be 'given' absolutely or specifically 'to someone'. A grammatical subject, as such, is an item whose presence does not result from a choice: the speaker, does not choose to use a subject or not, because, by definition, as it were, a subject, is what 'must' be added to a predicate to make a statement in those languages where we have a right to speak of a subject.
- Martinet (1962), Pag. 95-96