Internal and external evidence

Any linguist asked to provide candidate items for inclusion in a list of the slipperiest and most variably definable twentieth-century linguistic terms, would probably be able to supply several without much prompting. Often the lists would overlap (simplicity and naturalness would be reasonable prospects), but we would each have our own idiosyncratic selection. My own nominees are internal and external evidence.

In twentieth-century linguistics, types of data and of argument have moved around from one of these categories to the other relatively freely: but we can identify a general tendency for more and more types of evidence to be labelled external, a label to be translated ‘subordinate to internal evidence’ or, in many cases, ‘safe to ignore’. Thus, Labov (1978) quotes Kuryłowicz as arguing that historical linguistics should concern itself only with the linguistic system before and after a change, paying no attention to such peripheral concerns as dialect geography, phonetics, sociolinguistics, and psycholinguistics. Furthermore, in much Standard Generative Phonology, historical evidence finds itself externalised (along with ‘performance factors’ such as speech errors and dialect variation), making distribution and alternation, frequently determined by introspection, the sole constituents of internal evidence, and thus virtually the sole object of enquiry. In sum, ‘If we study the various restrictions imposed on linguistics since Saussure, we see more and more data being excluded in a passionate concern for what linguistics is not’ (Labov 1978: 275–6).