How did Matthew Arnold use Celtic literature in his lectures?

In his lectures titled On the Study of Celtic Literature (1867), Matthew Arnold utilized the "Celtic strain" primarily as a symbolic tool rather than through a rigorous academic or anthropological analysis of the subject.1

Lacking deep expertise in Celtic studies, Arnold employed the concept of the Celtic spirit to represent a resistance against the "despotism of the commonplace" and the utilitarian values he frequently criticized in Victorian society. By framing the Celtic influence in this way, he sought to contrast it with the prevailing attitudes of the "Philistines"—the commercial middle class he often challenged for their lack of intellectual and cultural depth. Ultimately, his use of Celtic literature served his broader critical project of advocating for a more refined, imaginative, and "cultured" approach to life in an age he perceived as suffering from spiritual discomfort and divided aims.123