For the further analysis of the language, the explicit record of descriptive (or, as they are called, phonemic) distinctions is as important as that of descriptive equivalences. If we have a body of text in a language, and do not know which segments in it are equivalent to each other (e.g. whether a 'g' in one line of the text is substitutable for a 'k' in another), we can do little in the way of further analysis. If we do not know which segment are distinct from each other, e.g. whether a word 'gam' in one line is distinguishable from a 'gam', or 'kam', in another, we still can do little analysis. When these two sets of data are explicitly given,however, it is possible to carry out the rest of the analysis. The fundamental data of descriptive linguistics are therefore the distinctions and equivalences among utterances and parts of utterances.
- Harris (1951), a pag.33