The role of prediction
From a classical WP perspective, the observation that morphology does not serve as a simple conduit for grammatical meaning does not entail that it is unnatural. Instead, this reflects the fact that morphology is a channel for broadcasting different kinds of information, including information about the shape of other forms in a system. By focussing solely on one of the factors that can condition morphological variation, Post-Bloomfieldian approaches (and those that have grown up in the shadow of the Post-Bloomfieldian tradition) create a false opposition between meaning-driven and ‘functionless’ variation.
The challenge for a general model lies in characterizing the role of morphemic and non-morphemic variation within a single system. Given that morphomes, by definition, are not susceptible to morphemic analysis, the only plausible unification is one that identifies the positive role of morphomes within a system and clarifies how morphemes would also function within this kind of system. The implicational structure of a classical WP model provides a suitably flexible relation. As suggested in Chapter 5.2, this flexibility derives from the fact that the units in a classical scheme of analysis are motivated by their predictive value, rather than solely by their grammatical content. In the classical tradition, the deduction of‘inflected’ (i.e. ‘bent’) forms from a basic form attached no significance to the sequences that were preserved or substituted in the deduction (Matthews 1994). Among the Neogrammarians, Paul (1920) was similarly agnostic about the status of the segmentations that guided proportional analogies, again as noted by Morpurgo Davies (1998). This structural agnosticism underlies the classical treatment of morphomic patterns in terms of interpredictability rather than interderivability. Cases of morphomic syncretism are intrinsically predictive, because it is their predictive character that makes them morphomic.
The predictive nature of Priscianic formations is emphasized in Matthews (1991). It is this predictive value that accounts for the function, and the perseverance and extension (Maiden 2005) of morphomic patterns:
For any Verb, however irregular it may be in other respects, the Present Infinitive always predicts the Imperfect Subjunctive. For the Verb ‘to flower’, florere ^ florerem; for the irregular Verb ‘to be,, esse ^ essem, and so forth without exception. (Matthews 1991:195, emphasis added)
A syncretic pattern is morphomic when it involves an implicational relation in which the shared ‘units of form’ do not correspond to shared ‘units of meaning’. It is only when the form correspondence is regular enough to sanction reliable predictions that it is recognized as a case of morphomic syncretism rather than fortuitous ambiguity. Hence morphomic patterns are not random “imperfections” that arise in “the mapping between morphosyntax and morphological realization” (Aronoff 1999:322). Instead, they serve to sanction deductions about the shape of other forms with different grammatical properties.
These deductions exploit the association between forms and paradigm cells. Pure forms in isolation are of limited predictive value. As the format of referral rules makes clear, it is forms under a given interpretation (i.e. cell-form pairs) that sanction useful deductions. The same is implicitly true of proportional analogies, which extend patterns defined by paradigm cells and principal parts, all of which contain forms with an interpretation. A predictive perspective applies equally to the simpler case of exponence rules, in which a set of features predicts a pattern of exponence. Morphemes fit just as neatly within a predictive model. A morpheme merely represents a type of symmetrical exponence relation in which the features predict the exponent and the exponent also predicts the features. Patterns that exhibit a biunique feature-form association are not only of value in identifying aspects of the grammatical meaning and function of a form, but also help to isolate other components of the form that may recur within a paradigm or elsewhere in the morphological system.
Implicational relations define the central predictive function that unites morphemic and morphomic elements in a morphological system. The composition and distribution of units can vary considerably across languages, but in all languages implicational relations provide a level of common organization. Hence these relations provide a more secure basis for a general morphological model than notions like ‘derivational’ relations, which can be seen as projecting an essentially diachronic relation onto a synchronic description in ways that offer no insight into the functioning of form variation within a system.