small aristocracy, whose rationale was based around warfare, a wider group of freemen, who had the right to bear arms and were represented in law codes, above a relatively large body of slaves, who may have lived beside and become clients of their owners. By the thirteenth century there are sources that allow greater stratification in society to be seen, with layers including the king and a small elite of mormaers above lesser ranks of freemen and what was probably a large group of serfs, particularly in central Scotland. In this period the feudalism introduced under David I meant that baronial lordships began to overlay this system, the English terms earl and thane became widespread. Below the noble ranks were husbandmen with small farms and growing numbers of cottars and gresemen with more modest landholdings. The combination of agnatic kinship and feudal obligations has been seen as creating the system of clans in the Highlands in this era. Scottish society adopted theories of the three estates to describe its society and English terminology to differentiate ranks. Serfdom disappeared from the records in the fourteenth century and new social groups of labourers, craftsmen and merchants, became important in the developing burghs. This led to increasing social tensions in urban society, but, in contrast to England and France, there was a lack of major unrest in Scottish rural society, where there was relatively little economic change. Culture Language and culture Modern linguists divide Celtic languages into two major groups, the P-Celtic, from which the Brythonic languages: Welsh, Breton, Cornish and Cumbric derive, and the Q-Celtic, from which come the Goidelic languages: Irish, Manx and Gaelic. The Pictish language remains enigmatic, since the Picts had no written script of their own and all that survives are place names and some isolated inscriptions in Irish ogham script. Most modern linguists accept that, although the nature and unity of Pictish language is unclear, it belonged to the former group. Historical sources, as well as place name evidence, indicate the ways in which the Pictish language in the north and Cumbric languages in the south were overlaid and replaced by Gaelic, Old English and later Norse in this period. By the High Middle Ages the majority of people within Scotland spoke the Gaelic language, then simply called Scottish, or in Latin, lingua Scotica. The Kingdom of Alba was overwhelmingly an oral society dominated by Gaelic culture.