The morpheme boundaries in an utterance are determined not on the basis of considerations interior to the utterance, but on the basis of comparison with other utterances. The comparisons are controlled, i.e., we do not merely scan various random utterances, but seek utterances which differ from our original one only in stated portions.
- Harris (1951), Pag. 163

Since the representation of an utterance or its parts is based on a comparison of utterances, it is really a representation of distinctions. It is this representation of differences which gives us discrete combinatorial elements (each representing a minimal difference). A non-comparative study of speech behavior would probably deal with complex continuous changes, rather than with discrete elements.
- Harris (1951), Pag. 367