Polarity is, the “choice between positive and negative” (H & M, p.116). The concept of polarity in general, and specifically the negative, doesn’t seem to get much attention or specific textbook treatment (except perhaps in old audio-lingual drills) but, as Halliday says, “choosing positive is just as substantive and meaningful as choosing negative” (H & M, p.143). Polarity is one way that allows speech functions to be arguable in terms of exchange by setting up an opposition between ‘yes’ and ‘no’: “either ‘is’ or ‘isn’t’ (proposition), either ‘do’ or ‘don’t’ (proposal)” (p.116).
The polarity may be attached to either the Finite (temporal or modal) or the proposition*. Thus we may have:
- I don’t have to go. (finite)
- I have to not go. (proposition)
Which may also be combined:
The difference between them may be shown with a question tag, where the unmarked form of the tag reverses the polarity. As such, if the polarity is attached to the Finite we get:
- She couldn’t have known, could she?
But if the polarity is attached to the proposition it becomes a distinct modal Adjunct and the tag is reversed:
- She could have not known, couldn’t she?
As a modal Adjunct, the polarity then has the ability to form a mood element itself, often in non-finite clauses for example:
- Not being funny but…
- Never having been myself…
It is also seen with a corresponding change in intonation:
However, polarity is most commonly associated with the Finite which “reflects the systemic association of polarity with mood” (H & M, p.143). This is shown in English with contracted forms where the “negative marker may be reduced to the point where positive and negative are more or less equivalent in weight” (H & M, p.143) and it is only the Finite element that allows this to happen. From this we can also see that reduced forms are more than just ‘sounding natural’ but represent a meaningful distinction.
*The choice of one or the other does seem to be affected by context: I’ve noticed that English spoken in the North of England, such as Liverpool, tends to focus more on the proposition in negative question forms (Did you not want to come?) while that spoken in the South focuses more on the Finite (Didn’t you want to come?). As EFL textbooks are largely based on upper middle-class language of the South this distinction tends to get overlooked.