[this is a piece of writing due to appear in my exibition, now to be held next thursday]
Jaques Lacan posited that there are three modalities of being; the real, the imaginary, and the symbolic. We all have ideas of our self, what we think we are like. Our internal selves can only be represented to others via the symbolic - through language. Thus, language is integral to our existence in the world. According to Lacan, you are not a being or subject if you cannot access the symbolic, for how would you constitute yourself? We call ourselves into being with the words 'I am'; we all have a representation in the symbolic - our names.
If language is this important, it follows that our voice is central to our state of being. In a sense it is the manifestation of the soul, or the imaginary in Lacanian terms, but what if you have no access to the symbolic or you have to access it through other means. The imaginary cannot be constituted fully in the symbolic, and therefore the subject is split completely. Moreover, the claim to subjectivity is lost. In a way you are not a person.
In part, this explains why people with no speech have historically been described as retarded, and locked away in institutions. To render this in Lacanian terms, this is because they have no access to the symbolic and therefore couldn't constitute themselves as subjects. Furthermore, if you use a communication aid, you constitute yourself through means other than your natural voice. This is why when we first met, my film lecturer asked me why I had an American accent. If you think about it, a guy born and bred in rural Cheshire speaking with an American accent is pretty weird. This is not to say I dislike my lightwriter, after all, it is the means through which I constitute myself. I just think it raises certain quirks when one tries to reconcile Lacan and lightwriter.