Matthew Arnold considers poets who possess "high seriousness" as those whose works exhibit profound moral insight, truth, and artistic excellence. In The Study of Poetry, he identifies the following poets as possessing this quality:
Homer
Dante
Shakespeare
Milton
These poets, according to Arnold, exemplify the highest standards of poetry and serve as "touchstones" for evaluating other works. Their poetry reflects deep intellectual and emotional power, making them timeless sources of wisdom and artistic greatness.