The language system tends toward efficiency and as such, struggles between states. Much like the making of tools, language has a tendency to keep the vocabulary that is already there however, new environments require new vocabulary so eventually, energy must be invested in restructuring aspects of syntax so that a lower energy state may be restored. Because the 2nd. law of thermodynamics tells us that the arrow of time is irreversible, the systems may revert to a low energy state, however it may do this only by generating a different configuration. In language the struggle is between vocabulary rich in perceptual cues - lexical - and vocabulary poor in perceptual cues but coherent enough in its role - functional. They are both stable energy states and they are both structurally different. Lexical vocabulary is easy to use because it is easy to describe but it is intolerant in allowing different instances of itself so it does not scale to other environments very easily. In other words, the work it can do is very limited but it is very coherent. Functional vocabulary is difficult but it is versatile and is more tolerant of different instances of itself and as such, it finds itself in many more environments. It can do more work but it is more incoherent in relationship to perceptual cues.