Knowles uses literary and Christian allusions (references) in A Separate Peace, showing that the students at the exclusive Devon school are steeped in Western culture.
Gene, for example, alludes to singing "A Mighty Fortress is our Home," a hymn by Martin Luther, and also mentions the German composer Beethoven, noting that Finny loved all kinds of music, from hymns to Beethoven. These allusions also suggest that though the US was at war with Germany, it was not traditional German culture the students felt they fought against, but the Nazis.
Finny asks Gene to read him some of the translating he is doing of Julius Caesar's work. Finny reads his translation of a part of Caesar's campaign against Gaul, summarizing it by saying "“He won it, if you really think there was a Gallic War . . . ” Although the text does not specify, Gene is probably reading Caesar's Commentarii de Bello Gallico. As Gene mentions, Finny does not "believe" in Caesar or his wars—or in World War II.
As for further Christian allusions, Gene likens Finny to Lazarus, brought back to life by God's touch, and, in the same passage, likens the beach to paradise: "white and stainless, as pure as the shores of Eden."