Halliday & Matthiessen (1999: 557)
How would we summarise the significance of indeterminacy, from the point of view of the semantic construal of experience? It lies first and foremost, perhaps, in the general principle that is being proclaimed, if indeterminacy is a typical and unremarkable feature of the grammar: that 'this is the way things are’. Our “reality” is inherently messy; it would be hard to construe experience, in a way that was beneficial to survival, with a semiotic system whose typical categories were well-defined, clearly bounded, and ordered by certainty rather than probability. This is the problem with designed systems, including semiotic ones: as a rule, they fail to provide adequately for mess.