Editing Nominative–accusative alignment (section)

===Functional pressure===

One theory that has been posited to account for the occurrence of accusative systems is that of functional pressure. When applied to languages, this theory operates around the various needs and pressures on a speech community. It has been suggested that languages have evolved to suit the needs of their users.These communities will develop some functional system to meet the needs that they have. So, it has been proposed that the accusative system arose from a functional pressure to avoid ambiguity and make communication a simpler process.<ref name=bates>Bates, E., & MacWhinney, B. (1982) ''Functionalist approaches to grammar''. In E.Wanner, & L. Gleitman (Ed.), ''Language acquisition: The state of the art''. New York:
Cambridge University Press.</ref><ref name=fedz>Fedzechkina, Maryia & Jaeger, T. Florian & Newport, Elissa L. (2011) "Functional Biases in Language Learning: Evidence from Word Order and Case-Marking Interaction". ''Cognitive Science''.</ref>

It is useful for languages to have a means of distinguishing between subjects and objects, and between arguments A, S, and O. This is helpful so that sentences like "Tom hit Fred" cannot be interpreted as "Fred hit Tom." [[tripartite language|Tripartite]] alignment systems accomplish this differentiation by coding S, A and O all differently. However, this is not structurally economical, and tripartite systems are comparatively rare, but to have all arguments marked the same makes the arguments too ambiguous. Alongside the principle of distinguishability seems to operate a principle of economy. It is more efficient to have as few cases as possible without compromising intelligibility. In this way the dual pressures of efficiency and economy have produced a system which patterns two kinds of arguments together a third separately. Both accusative and ergative systems use this kind of grouping to make meaning clearer.

<!---Preliminary kept here for further use in other articles
==Sociolinguistics and nominative–accusative alignment==  
{{Off topic|date=May 2020}}
===Collapse of English second-person pronouns===
{| align=left class="wikitable" style="margin-right:2em"
! Case
! Old English
! Early Modern English
! Modern English
|-
! SG <small>[[Nominative case|NOM]]</small>
| þu || thou || you
|-
! SG <small>[[Accusative case|ACC]]</small>
| þe || thee || you
|-
! SG DAT
| þe || thee || you
|-
! SG GEN
| þin || thy/thine || your
|-
! PL <small>[[Nominative case|NOM]]</small>
| ge || ye || you
|-
! PL <small>[[Accusative case|ACC]]</small>
| eow || you || you
|-
! PL DAT
| eow || you || you
|-
! PL GEN
| eower || your || your
|}

Because pronominal reference systems to the speaker, addressee, and a third person are so common (some argue [[universal grammar|universal]]) cross-linguistically, it would seem that pronoun systems are quite stable. However, the changes involved in [[grammatical person|second-person]] pronouns in English call this stability into question and highlight the significance of social forces in language development. The spread of [[feudalism|feudalistic]] ideology caused many European languages to develop two sets of second-person singular pronouns in order to reflect hierarchy. Therefore, pronouns encoded not only person or number, but also the speaker's assessment of the addressee's status and the speaker-addressee relationship.

From the thirteenth century, the [[Middle English]] plural pronouns 'ye' (nominative) and 'you' (accusative) were used to address single individuals in upper-class or courtly contexts.<ref name=nau>Fitzmaurice, Susan. "Politeness in Early Modern English". http://jan.ucc.nau.edu/~eng121-c/politenessin%20AME.htm</ref> As a result, there were two sets of second-person singular pronouns, and the alternative singular pronouns 'thou' (nominative) and 'thee' (accusative) became increasingly associated with lower status. These distinctions had become established indices of social status by the fifteenth century, and they also developed as indicators of interpersonal relationships at this time: 'you' might show emotional distance or be used in a public setting, 'thou' familiarity/intimacy in a private setting.<ref name=nau/> We see vestiges of this distinction in languages like German or French that have retained the [[T-V distinction]], but second-person pronouns in these languages, as well as in Italian, Serbo-Croatian, and Swedish, have also begun to undergo change.<ref name=feminist>Cameron, Deborah. (1998) ''The feminist critique of language: a reader''. Psychology Press.</ref>

Under the pressure of social structural changes and movement towards [[egalitarianism|egalitarian]] ideology, the English second-person singular pronouns later collapsed to a single term, 'you'.<ref name=feminist/> This contraction erased all visible morphological distinction between nominative and accusative case in the second person, effectively sacrificing distinguishability for economy.--->