How is the title, "The Doors of Life," significant?

Sandy was wondering more and more about sex and Tempy had given him a book about it called "The Doors of Life" written by a white Presbyterian Minister from New England. The book didn't help Sandy; in fact, he rebelled against it because he thought some white minister could never understood what he and his friends endured. This title of both the chapter and the book show how different the white culture that Tempy finds important has no place in Sandy's life.