In Chapter 3 of The Chocolate War, the word "Why?" had been scrawled in "a blank space no advertiser had rented" on the side of the bus. Beneath that word, someone "had slashed in answer" the words "Why not?"
Jerry is an intelligent young man, and the words scribbled on the side of the bus make him think about the reasons he does the things he does. In the liberated, freedom-loving society of the late 1960s and early 1970s, his school, Trinity, is "one of the last schools to retain a dress code - shirt and tie," and it also demands complete comformity in a number of other ways as well. The students are expected to behave according to a strict standard of behavior at all times, and to submit unquestioningly to directives such as participating in the school candy sale. The questions on the side of the bus reflect thoughts going on already in Jerry's mind. Unlike so many of his classmates, he does not easily submit mindlessly to whatever he is told to do. He is prone to reflection, and consideration of the possibility of acting on his own, in defiance of the established order.
Just before he sees the writing on the bus, Jerry is confronted by a hippie who is hanging out with a group on the Common across the street. The hippie mocks him for his obvious adherence to convention, chiding,
"You know who's sub-human, man? You. You are. Going to school every day. And back home on the bus. And do your homework...square boy. Middle-aged at fourteen, fifteen. Already caught in a routine. Wow."
Although Jerry is not inclined to drop out of society to the extent done by the hippie and his companions, he is being challenged on all sides to at least think about what he does in his life. By doing so, however, he is taking a great risk, because in the world in which he lives, refusing conform, even through such seemingly insignificant means as not participating in his school's candy sale, brings dire consequences (Chapter 3).