“The formal quality of everry piece of typography depends on the relationship between the printed and unprinted parts. To see only what is printed, to overlook the decisive contribution of the unprinted parts, is a sign of professional immaturity. The business of typography is a continual weighing up of white and black, which requires a thorough knowledge of the laws governing optical values.”

—Emil Ruder, from Typography as Communication and as Form, 1960; quoted in Swiss Graphic Design by Richard Hollis, 2006.