An allusion is a reference made to someone or something that the reader, or a character, might know or understand. This helps to extract familiar knowledge about a topic and apply it to the story at hand to understand a specific point or theme more profoundly. For example, in Chapter One of A Separate Peace, Gene walks down Gilman Street and describes it for the reader. He says the following:
"The houses were as handsome and as unusual as I remembered. Clever modernizations of old Colonial manses, extensions in Victorian wood, capacious Greek Revival temples line the street" (10).
The above passage alludes to three different historical time periods in an effort to describe the setting and what the houses look like.
Next, when Gene finds the infamous tree from which he and Phineas jumped so many times that summer of 1942, he says the following:
"It had loomed in my memory as a huge lone spike dominating the riverbank, forbidding as an artillery piece, high as the beanstalk" (13).
With this description there are a couple of similes that help the allusion develop fully. First, "an artillery piece" refers to an offensive piece of military hardware or a battlement. This is a strong, and possibly violent, reference to war or fighting. Then, the allusion to "the beanstalk" refers to the familiar tale of "Jack and the Beanstalk." This brings to mind an image of a very tall, powerful, and almost immeasurable plant.
A third allusion in Chapter One is made when Phineas and Gene are hurrying back for dinner. They are about to be late if they don't hurry, so Gene starts to walk faster. Phineas calls this Gene's "West Point stride" (18). West Point is the United States' military academy. This reference brings to mind soldiers obediently, stiffly, but probably quickly falling into line without completely running.