Steps in the comparative method

The information given in the previous paragraphs is intended to illustrate what is meant by a sound law and to indicate the kind of considerations that are taken into account in the application of the comparative method. The first step is to find sets of cognate or putatively cognate forms in the languages or dialects being compared: for example, Latin decem = Greek deka = Sanskrit daśa = Gothic taihun, all meaning “ten.” From sets of cognate forms such as these, sets of phonological correspondences can be extracted; e.g., (1) Latin d = Greek d = Sanskrit d = Gothic t; (2) Latin e = Greek e = Sanskrit a = Gothic ai (in the Gothic orthography this represents an e sound); (3) Latin c (i.e., a k sound) = Greek k = Sanskrit ś = Gothic h; (4) Latin em = Greek a = Sanskrit a = Gothic un. A set of “reconstructed” phonemes can be postulated (marked with an asterisk by the standard convention) to which the phonemes in the attested languages can be systematically related by means of sound laws. The reconstructed Proto-Indo-European word for “ten” is *dekm. From this form the Latin word can be derived by means of a single sound change, *m changes to em (usually symbolized as *m > em); the Greek by means of the sound change *m > a (i.e., vocalization of the syllabic nasal and loss of nasality); the Sanskrit by means of the palatalizing sound law, *k > ś and the sound change *m > a (whether this is assumed to be independent of the law operative in Greek or not); and the Gothic by means of Grimm’s law (*d > t, *k > h) and the sound change *m > un.

Most 19th-century linguists took it for granted that they were reconstructing the actual word forms of some earlier language, that *dekm, for example, was a pronounceable Proto-Indo-European word. Many of their successors have been more skeptical about the phonetic reality of reconstructed starred forms like *dekm. They have said that they are no more than formulae summarizing the correspondences observed to hold between attested forms in particular languages and that they are, in principle, unpronounceable. From this point of view, it would be a matter of arbitrary decision which letter is used to refer to the correspondences: Latin d = Greek d = Sanskrit d = Gothic t, and so on. Any symbol would do, provided that a distinct symbol is used for each distinct set of correspondences. The difficulty with this view of reconstruction is that it seems to deny the very raison d’être of historical and comparative linguistics. Linguists want to know, if possible, not only that Latin decem, Greek deka, and so on are related, but also the nature of their historical relationship—how they have developed from common ancestral form. They also wish to construct, if feasible, some general theory of sound change. This can be done only if some kind of phonetic interpretation can be given to the starred forms. The important point is that the confidence with which a phonetic interpretation is assigned to the phonemes that are reconstructed will vary from one phoneme to another. It should be clear from the discussion above, for example, that the interpretation of *d as a voiced dental or alveolar stop is more certain than the interpretation of *k as a voiceless velar stop. The starred forms are not all on an equal footing from a phonetic point of view.