Halliday (2008: 126):
To revisit my earlier analogy of climate and weather: the power of weather to influence our daily lives, through storms and floods and droughts and all the rest, derives from the fact that it is the instantiation of something we call “climate” — because it is climate that has shaped our evolution and so determines the effect on us, and indeed on all of nature, of all the fluctuating processes and forces that we call “weather”. In the same way the power of the text resides in the system, because it is the system that determines the meaning and the significance of the ongoing choices made by writers and speakers. It is a mistake to restrict our angle of vision to just one perspective or the other, or to treat the discourse analyst and grammarian as if they inhabited two different realms of intellectual being.