Halliday & Matthiessen (1999: 523):
Our concern in this book is primarily with what we have called the "ideation base", the systems of meaning into which, through language, human beings construe their collective and individual experience. Usually when we talk about the linguistic "construction of reality" this is the aspect of reality that comes to mind. But at the same time as construing experience — in the same breath, so to speak — they are also, through language, enacting their interpersonal relationships; and this interpersonal component of meaning is no less part of what is constituted for us as "reality". If the ideational component is language as a mode of reflection, the interpersonal component is language as a mode of action; and reality consists as much in what we do as in what we think.