There exists a solidarity among all the performances of the same phoneme which tends to preserve its identity whatever the sense of the word may be. The phonic environments may result in distortions of warpings away from that performance of the phoneme in isolation. But the semantic context is normally powerless. All this is, nothing but synchronic version of the regularity of phonetic changes: only in very particular cases, which should be especially accounted for, many meaning affect phonetic evolution. This phonematic solidarity can only be explained if we conceive of the phoneme as an articulatory habit, something we should always keep in mind, even if we choose to disregard it temporarily when concentrating on descriptive methods.
- Martinet (1962), Pag. 24-25