[...] The English tone system is based on an opposition between falling and rising pitch, in which falling pitch conveys certainty and rising pitch uncertainty. The falling/rising opposition is the most fundamental one there is, and it probably plays some part in the system of every language, though with vast differences among different languages in its scope and value in the system. In English, where it plays a very important part indeed, the meaning relates rather specifically to POLARITY, the positive / negative opposition. Thus falling pitch means ʻpolarity knownʼ, while rising pitch means ʻpolarity unknownʼ.
- Halliday (1985), a pag.281