And now we come to the Heart of our Designe: the art of Shaddowes you must know well, Walter, and you must be instructed how to Cast them with due Care. It is only the Darknesse that can give trew Forme to our Work and trew Perspective to our Fabrick, for there is no Light without Darknesse and no Substance without Shaddowe (and I turn this Thought over in my Mind: what Life is there which is not a Portmanteau of Shaddowes and Chimeras?). I build in the Day to bring News of the Night and of Sorrowe, I continued, and then I broke off for Walter's sake.