At first sight, it seems obvious that speech has priority over writing; that the former is the central linguistic phenomenon while the latter is merely a device for capturing speech in a less transient form and permitting its diffusion beyond the temporal or spatial reach of an individual voice. This is, of course, a simplification. Many texts — for instance this book — are unlikely to have originated first as continuous spoken utterances and then been written down. Because what is written is preserved, it can be revised, collated, organised and connected with other moments of writing to generate a continuous discourse that could not have conceivably been produced in a single stretch of speech. This does not, however, impugn the priority of speech; the written text can still be plausibly regarded as the accumulation of many moments of actual speech (as in a transcript) or of potential speech (as in a text written over many years).