Why did Scottish Gaelic remain strong in the Hebrides compared with much of mainland Scotland?

Scottish Gaelic has maintained a stronger presence in the Hebrides compared to the Scottish mainland primarily due to the geographical and cultural isolation of the islands, which shielded them from the rapid linguistic shifts occurring elsewhere.1

While the "Highland Line"—a boundary between the Gaelic-speaking Highlands and the English-speaking (Scots) Lowlands—has steadily receded westward since medieval times, the mainland faced intense pressure from northern dialects of English (Scots) from the beginning. In contrast, the Hebrides remained more insulated from these external linguistic influences.1

Furthermore, the survival of the language in the region is linked to the strong tradition of literacy among Gaelic-speaking Protestants, who were accustomed to reading the Bible and using the vernacular in religious services. Although Gaelic is now largely confined to the home in the Hebrides, it remains a mother tongue for its speakers, whereas on the mainland, the language has largely disappeared or been replaced by English. While the mainland has seen a literary revival, it is often driven by displaced speakers in urban centers like Glasgow and Edinburgh rather than the traditional heartlands.1