What is the theme in The Long Loneliness: The Autobiography of Dorothy Day by Dorothy Day?

Loneliness is a theme in this book. Day began her childhood spending much of her time alone. Her father worked long hours as a writer and journalist, and due to his low income, Day's mother had to work constantly as well. Thus, while she sometimes played with her brothers and sisters, she spent a lot of time alone and outside. It was here that she developed a deep love of nature and that her natural disposition towards religiosity grew. When Day left to go to the University of Illinois, she left her family for the first time, and when she left Illinois, she was alone in New York. During this time, Day developed a conception of loneliness that she calls The Long Loneliness.