This document summarizes a lecture about Longinus, a 1st century AD writer known for his work On the Sublime. The lecture discusses that Longinus wrote On the Sublime in response to another writer, investigating the main sources of good writing and being the first to emphasize the natural gift of writers. It then outlines Longinus' five sources of sublimity - grandeur of thought, capacity for strong emotions, appropriate use of figures, nobility of diction, and dignity of composition. Each source is then briefly described.