In historical linguistics, internal reconstruction is a method of reconstructing an earlier state in a language's history using only evidence internal to the language in question.
The comparative method compares variations between languages, such as in sets of cognates, under the assumption that they descend from a single proto-language, but internal reconstruction compares variant forms within a single language under the assumption that they descend from a single, regular form. For example, they could take the form of allomorphs of the same morpheme.
The basic premise of internal reconstruction is that a meaning-bearing element that alternates between two or more similar forms in different environments was probably once a single form into which alternation has been introduced by the usual mechanisms of sound change and analogy.
Language forms that are reconstructed by internal reconstruction are denoted with the pre- prefix, as in Pre-Old Japanese, like the use of proto- to indicate a language reconstructed by means of the comparative method, as in Proto-Indo-European. (However, the pre- prefix is sometimes used for an unattested prior stage of a language, without reference to internal reconstruction.)
It is possible to apply internal reconstruction even to proto-languages reconstructed by the comparative method. For example, performing internal reconstruction on Proto-Mayan would yield Pre-Proto-Mayan. In some cases, it is also desirable to use internal reconstruction to uncover an earlier form of various languages and then submit those pre- languages to the comparative method. Care must be taken, however, because internal reconstruction performed on languages before the comparative method is applied can remove significant evidence of the earlier state of the language and thus reduce the accuracy of the reconstructed proto-language.
Role in historical linguistics When undertaking a comparative study of an underanalyzed language family, one should understand its systems of alternations, if any, before one tackles the greater complexities of analyzing entire linguistic structures. For example, Type A forms of verbs in Samoan are the citation forms, which are in dictionaries and word lists, but in making historical comparisons with other Austronesian languages, one should not use Samoan citation forms that have missing parts. (An analysis of the verb sets would alert the researcher to the certainty that many other words in Samoan have lost a final consonant.)
In other words, internal reconstruction gives access to an earlier stage, at least in some details, of the languages being compared, which can be valuable since the more time has passed, the more changes have been accumulated in the structure of a living language. Thus, the earliest known attestations of languages should be used with the comparative method.
Internal reconstruction, when it is not a sort of preliminary to the application of the comparative method, is most useful if the analytic power of the comparative method is unavailable, especially in language isolates.
Internal reconstruction can also draw limited inferences from peculiarities of distribution. Even before comparative investigations had sorted out the true history of Indo-Iranian phonology, some scholars had wondered if the extraordinary frequency of the phoneme in Sanskrit – 20% of all phonemes together – might point to some historical fusion of two or more vowels. (In fact, it represents the final outcome of five different Proto-Indo-European syllabics whose syllabic states of and can be discerned by the application of internal reconstruction.) However, in such cases, internal analysis is better at raising questions than at answering them. The extraordinary frequency of in Sanskrit hints at some sort of historical event but does not and cannot lead to any specific theory.
Issues and shortcomings Neutralizing environments One issue in internal reconstruction is neutralizing environments, which can be an obstacle to historically correct analysis. Consider the following forms from Spanish, spelled phonemically rather than orthographically:
Infinitive Third person singular bolbér (re)turn buélbe probár test pruéba dormír sleep duérme morír die muére ponér place póne doblár fold dóbla goθár enjoy góθa korrér run kórre
One pattern of inflection shows alternation between and ; the other type has throughout. Since those lexical items are all basic, not technical, high-register or obvious borrowings, their behavior is likely to be a matter of inheritance from an earlier system, rather than the result of some native pattern overlaid by a borrowed one. (An example of such an overlay would be the non-alternating English privative prefix un- compared to the alternating privative prefix in borrowed Latinate forms, in-, im, ir-, il-.)
One might guess that the difference between the two sets can be explained by two different native markers of the third-person singular, but a basic principle of linguistic analysis is that one cannot and should not try to analyze data that one does not have. Also, positing such a history violates the principle of parsimony (Occam's Razor) by unnecessarily adding a complication to the analysis whose chief result is to restate the observed data as a sort of historical fact. That is, the result of the analysis is the same as the input. As it happens, the forms as given yield readily to real analysis and so there is no reason to look elsewhere.
The first assumption is that in pairs like bolbér/buélbe, the root vowels were originally the same. There are two possibilities: either something happened to make an original turn into two different sounds in the third-person singular, or the distinction in the third-singular is original and the vowels of the infinitives are in what is called a (if an original contrast is lost because two or more elements "fall together", or coalesce into one). There is no way of predicting when breaks to and when it remains in the third-person singular. On the other hand, starting with and , one can write an unambiguous rule for the infinitive forms: becomes . One might notice further, upon looking at other Spanish forms, that the nucleus is found only in stressed syllables even other than in verb forms.
That analysis gains plausibility from the observation that the neutralizing environment is unstressed, but the nuclei are different in stressed syllables. That fits with vowel contrasts often being preserved differently in stressed and unstressed environments and that the usual relationship is that there are more contrasts in stressed syllables than in unstressed ones since previously-distinctive vowels fell together in unstressed environments.
The idea that original might fall together with original is unproblematic and so internally, a complex nucleus *ue can be reconstructed that remains distinct when it is stressed and coalesces with *o when it is unstressed.
However, the true history is quite different: there were no diphthongs in Proto-Romance. There was an (reflecting Latin ŭ and ō) and an (reflecting Latin ŏ). In Spanish the two fell together in unstressed syllables, as in all other Romance languages, but broke into the complex nucleus in stressed syllables. Internal reconstruction accurately points to two different historical nuclei in unstressed but gets the details wrong.
Shared innovations When applying internal reconstruction to related languages prior to applying the comparative method, one must check that the analysis does not remove the shared innovations that characterize subgroups. An example is consonant gradation in Finnish, Estonian, and Sami. A pre-gradation phonology can be derived for each of the three groups by internal reconstruction, but it was actually an innovation in the Finnic branch of Uralic, rather than the individual languages. Indeed, it was one of the innovations defining that branch. That fact would be missed if the comparanda of the Uralic family included as primary data the "degraded" states of Finnish, Estonian, and Sami.Campbell (2013), pp. 211–212.
Lost conditioning factors Not all synchronic alternation is amenable to internal reconstruction. Even if a secondary split (see phonological change) often results in alternations that signal a historical split, the conditions involved are usually immune to recovery by internal reconstruction. For example, the alternation of voiced and voiceless fricatives in Germanic languages, as described in Verner's law, cannot be explained only by examining the Germanic forms themselves.
Despite that general characteristic of secondary split, internal reconstruction can occasionally work. A primary split is, in principle, recoverable by internal reconstruction whenever it results in alternations, but later changes can make the conditioning irrecoverable.
Examples
English English has two patterns for forming the past tense in roots ending in apical stops: .
+ Type I Present Past adapt adapted fret fretted greet greeted note noted reflect reflected regret regretted rent rented wait waited waste wasted abide abided blend blended end ended found founded fund funded grade graded plod plodded + Type II Present Past cast cast cut cut put put set set meet met bleed bled read /riːd/ read /rɛd/ rid rid shed shed bend bent lend lent send sent
Although Modern English has very little affixal morphology, its number includes a marker of the preterite, other than verbs with vowel changes of the find/found sort, and almost all verbs that end in take as the marker of the preterite, as seen in Type I.
Comparing between the verbs of Type I and Type II, those in Type II are all basic vocabulary (This is a claim about Type II verbs and not about basic verbs since there are basic verbs in Type I also). However, no denominative verbs (those formed from nouns like to gut, to braid, to hoard, to bed, to court, to head, to hand) are in Type II. There are no verbs of Latin or French origin; all stems like depict, enact, denote, elude, preclude, convict are Type I. Furthermore, all new forms are inflected as Type I and so all native speakers of English would presumably agree that the preterites of to sned and to absquatulate would most likely be snedded and absquatulated.
That evidence shows that the absence of a "dental preterite" marker on roots ending in apical stops in Type II reflects a more original state of affairs. In the early history of the language, the "dental preterite" marker was in a sense absorbed into the root-final consonant when it was or , and the affix after word-final apical stops then belonged to a later stratum in the evolution of the language. The same suffix was involved in both types but with a total reversal of "strategy." Other exercises of internal reconstruction would point to the conclusion that the original affix of the dental preterites was (V being a vowel of uncertain phonetics). A direct inspection of Old English would certainly reveal several different stem-vowels involved. In modern formations, stems that end in preserve the vowel of the preterite marker. The loss of the stem vowel had taken place already whenever the root ended in an apical stop before the first written evidence.
Latin