What did Matthew Arnold mean by high seriousness in poetry?

In his essay "The Study of Poetry," Matthew Arnold introduced the concept of "high seriousness" as a standard for evaluating the quality of poetry.1

For Arnold, high seriousness refers to a profound, noble, and morally earnest quality found in the works of acknowledged literary masters. He argued that in an era of "crumbling creeds," poetry should serve as a vital source of interpretation, consolation, and sustenance for the human spirit. To distinguish genuine, superior poetry from inferior or "counterfeit" work, Arnold proposed using specific passages from these masters as "touchstones". These touchstones exemplify both high seriousness and a superior quality of diction and movement, serving as a benchmark to measure the value of other poetic works.1

Ultimately, this criterion was part of Arnold’s broader belief that poetry is "at bottom a criticism of life," provided it adheres to the laws of poetic truth and beauty. By emphasizing high seriousness, he sought to elevate literature as a means to provide moral and intellectual "deliverance" for the modern world.12