Longinus's purpose in On the Sublime is to analyze and promote a "certain loftiness and excellence of language." The primary goal of this lofty or literary language of sublimity is not to provide rational and persuasive arguments on a topic but to move the emotions of readers or audiences.

To do this, successful writers must aim high and take risks to emotionally transport their audiences. However, while many will say, according to Longinus, that great writing springs from geniuses whose gifts are inborn and can't be taught, Longinus pushes back. Inborn intelligence and genius are a factor in great writing, he says, but it is also very important as well as fruitful to learn the rules of writing and rhetoric and to master the principles of literary language, including metaphors and figures of speech.

To emotionally transport the reader means to avoid common pitfalls. For example, everyday language or worn-out phrases are not going to work. At the same time, the writer should learn to sidestep inflated language, which is

one of the hardest things to avoid in writing. For all those writers who are ambitious of a lofty style, through dread of being convicted of feebleness and poverty of language, slide by a natural gradation into the opposite extreme.

These types of misfires are ridiculous and fail to transport an audience, because such language is "hollow" and based on false emotions. The elevated language being used is not tied sufficiently to the reality of the situation being described. "Grandeur of thought," the basis of the sublime, must be rooted in reality and then converted into a language that accurately but passionately describes truth. Then the emotions of an audience will then be engaged and transported.

How does elevated language affect the audience in Longinus's On the Sublime?

This is an intriguing question to consider because Longinus in his treatise opens up the debate about whether achieving excellence in literature (which he defines as sublimity) is a result of natural genius or learnt skill and artifice. On the one hand Longinus, in opening up this debate, quotes critics who argue that a "lofty tone" is "innate." He quotes what is obviously some sort of maxim or creed from his day to support this view:

Works of nature are, they think, made worse and altogether feebler when wizened by the rules of art.

Such critics therefore believe that it is transport that causes the effect of elevated language upon the audience, as persuasion is a skill that is based on learnt rhetoric and not something that is innate and instinctive, a result of natural genius. However, Longinus interestingly takes a middle ground in this debate, arguing that both "nature" and "system" have their rightful place in the creation of sublimity:

While nature as a rule is free and independent in matters of passion and elevation, yet is she wont not to act at random and utterly without system.

Achieving elevated language therefore necessarily involves transport, but part of that achievement also involves persuasion, as learnt skill hs its place in helpfully curbing innate genius and natural expression. In short, Longinus argues through his emphasis both on "nature" and on "system" that elevated language has the effect primarily of transport, but that persuasion is a secondary and important effect as well. The truly excellent author is able to recognise when he or she needs to use rhetoric and other learnt skills to curb their unbridled genius.