National literature treats questions confined to one nation.
Comparative literature deals with problems involving two different literatures.
General literature is devoted to developments in a large numbers of countries making up organic units, such as Western Europe, North America, etc. (e.g., Curtius, European Literature and the Latin Middle Ages)
National literature: study of literature within walls
Comparative literature: study of literature across walls
General literature: study of literature above walls
There is agreement on its task: to give a better, more comprehensive understanding of literature as a whole rather than of a departmental fragment or several isolated departmental fragments of literature. It can do so best by not only relating several literatures to each other but by relating literature to other fields of human knowledge and activity, especially artistic and ideological fields; that is, by extending the investigation of literature both geographically and generically.
A paper on the historical sources of a Shakespearean drama would (unless it concentrates on another country) be "comparative lietarature" only if historiography and literature were the main poles of the investigation, if historical facts or accounts and their literary adaptations were systematically compared and evaluated, and conclusions arrived at which would bear on the two domains as such. A treatment of the role of money in Balzac's Pegre Goriot would be comparative only if it were principally (not just incidentally) concerned with the literary osmosis of a coherent financial system or set of ideas. A inquiry into the ethical or religious ideas of Hawthorne or Melville could be considered comparative only if it dealt with an organized religious movement (e.g., Calvinism) or set of beliefs. The tracing of a character in a novel by Henry James would be within the scope of comparative literature only if it developed a methodical view of this character in the light of the psychological theories of Freud (or Adler, Jung, etc.).