Another method that has yielded new results is the generalization of operations from one operand to another. If the classification of complementary variants when applied to phonemic segments yields phonemes, it can be applied to morphemic segments to yield morphemes. If the independence of a sequence of contiguous phonemes establishes it as a morpheme, we can also set up any sequence of non-contiguous phonemes or any interchange of phonemes as a morpheme so long as it is equally independent of the other morphemes. If morphemes which substitute for each other are considered equivalent from the point of view of the utterance, so are morpheme sequences which substitute for them. In all these cases the operation is not changed, the old operand becomes a special case of a new and larger class of operands. In many cases it is at first impossible to obtain the desired results completely. The operation may then be carried out first in a simplified form, or on a selected set of operands, and the approximation obtained from these first results may then be corrected or extended by repeated carrying out of the operation.
- Harris (1951), a pag.371