The notion of the sublime stretches back to the Greek philosopher Longinus who produced a theory that attributed strong emotional responses to how orators used various techniques in rhetoric. In the eighteenth century, the Romantic sublime came alive when Longinus's idea of the sublime was reawakened and connected, not to rhetoric in powerful speeches, but to the emotive affect and epiphanic affect of grand sights in nature. The Romantic sublime focused on how a gnarled tree or a sweeping, wind-torn vista could awaken feelings of awe and create a connection in the observer with the greatness of nature. In Sense and Sensibility, Austen alludes to this when Edward tells Marianne and Elinor:
I have no knowledge in the picturesque, and I shall offend you by my ignorance and want of taste .... I shall call hills steep, which ought to be bold; surfaces strange and uncouth, which ought to be irregular and rugged; and distant objects out of sight, which ought only to be indistinct through the soft medium of a hazy atmosphere.
The Gothic sublime differs in that Edmund Burke wrote a book that tied the sublime--the emotional power of a strong effect--to negative and dark emotions. Thus, Gothic sublime uses nature, locations, and personas to create the sublime of fear, horror, dread, and suspense.
Therefore, the sublime is the aesthetic of a psychological impact of a significant effect. At first, Longinus tied this impact, this sublime, to an inspiring affect from rhetoric used in great speeches. Then in the eighteenth century, writers and philosophers tied this impact to an inspiring affect from nature and the supernatural (angels, ghosts, etc), thus creating the Romantic sublime. Finally, Burke gave rise to the Gothic sublime by tying this impact to an unnerving affect from dark and eerie nature, places, and personas for the express purpose of producing horror, fear, dread, and suspense.