The book's opening line, "The cradle rocks above an abyss, and common sense tells us that our existence is but a brief crack of light between two eternities of darkness," is arguably a paraphrase of Thomas Carlyle's "One Life; a little gleam of Time between two Eternities," found in Carlyle's 1840 lecture "The Hero as Man of Letters," published in On Heroes, Hero-Worship, and The Heroic in History in 1841. There is also a similar concept expressed in "On the nature of things" by the Roman Poet Lucretius. The line is parodied at the start of "Little Wilson and Big God", the autobiography of the English writer Anthony Burgess. "If you require a sententious opening, here it is. Wedged as we are between two eternities of idleness, there is no excuse for being idle now."