Longinus opens his inquiry by challenging earlier critical works that reduce the sublime to mere mechanical rules. He argues that true sublimity originates in nobility of soul and natural genius, which must be guided rather than stifled by artistic method. The author identifies five primary sources of literary greatness: grandeur of thought, powerful passion, the strategic use of figures of speech, noble diction, and dignified composition.
The treatise details specific stylistic elements, such as the selection of striking details in poetry, the effective employment of metaphors, and the arrangement of words to produce an irresistible cadence. Longinus illustrates these points using extensive examples from Homer, Plato, and the Attic orators, contrasting genuine sublimity with common vices of style like bombast, false sentiment, and frigidity.
A significant portion of the work is dedicated to examining faults in great authors, distinguishing between minor oversights of adventurous genius and the safe mediocrity of writers who never stumble. Longinus maintains that bold excellence is always preferable to tame correctness.
In the concluding section, the author addresses a broader philosophical question concerning the apparent decay of literary genius in his contemporary world. Rather than blaming political despotism alone, he points to human failings such as the consuming pursuit of wealth and pleasure as the true causes of moral and intellectual decline.
The text survives only in fragmentary form, leaving questions of its precise date and authorship open to scholarly debate. Nevertheless, it remains one of the most enduring works of literary criticism from the ancient world.