For 1,500 years, Scottish Gaelic literature had developed a rich corpus of song and poetry across "literary, sub-literary, and non-literate" registers; it retained the ability to convey "an astonishingly wide range of human experience". MacLean's work drew on this "inherited wealth of immemorial generations"; according to MacInnes, few people were as intimately familiar with the entire corpus of Gaelic poetry, written and oral, as MacLean. In particular, MacLean was inspired by the intense love poetry of William Ross, written in the eighteenth century. Of all poetry, MacLean held in highest regard the Scottish Gaelic songs composed before the nineteenth century by anonymous, illiterate poets and passed down via the oral tradition. He once said that Scottish Gaelic song-poetry was "the chief artistic glory of the Scots, and of all people of Celtic speech, and one of the greatest artistic glories of Europe".