This thesis focuses on the historical development of dialectal variation in the Gaelic
languages with special reference to Irish. As a point of departure, competing
scholarly theories concerning the historical relationships between Goidelic dialects
are laid out. Next, these theories are tested using dialectometric methods of linguistic
analysis. Dialectometry clearly suggests the Irish of Ulster is the most linguistically
distinctive of Irish dialects. This perspective on the modern dialects is utilised in
subsequent chapters to clarify our understanding of the history of Gaelic dialectal
variation, especially during the Old Irish period (AD 600–900).
Theoretical and methodological frameworks that have been used in the study of the
historical dialectology of Gaelic are next outlined. It is argued that these frameworks
may not be the most appropriate for investigating dialectal variation during the Old
Irish period. For the first time, principles from historical sociolinguistics are here
applied in investigating the language of the Old Irish period. In particular, the social
and institutional structures which supported the stability of Old Irish as a text
language during the 8th and 9th centuries are scrutinised from this perspective. The
role of the ecclesiastical and political centre of Armagh as the principal and central
actor in the relevant network structures is highlighted.
Focus then shifts to the processes through which ‘standard’ languages emerge, with
special reference to Old Irish. The evidence of a small number of texts upon which
modern understandings of Old Irish was based is assessed; it is argued that these
texts most likely emerged from monasteries in the northeast of Ireland and the
southwest of Scotland. Secondly, the processes through which the standard of the
Old Irish period is likely to have come about are investigated. It is concluded that the
standard language of the period arose primarily through the agency of monastic
schools in the northeast of Ireland, particularly Armagh and Bangor. It is argued that
this fact, and the subsequent prominence of Armagh as a stable and supremely
prestigious centre of learning throughout the period, offers a sociolinguistically
robust explanation for the apparent lack of dialectal variation in the language.
Finally, the socio-political situation of the Old Irish period is discussed. Models of
new-dialect formation are applied to historical evidence, and combined with later
linguistic evidence, in an attempt to enunciate dialectal divisions which may have
existed during the period