Eagleman has said he drew inspiration for Sum from two books: Alan Lightman's Einstein's Dreams and Italo Calvino's Invisible Cities. Both books explore the temporality of time and space, pushing the reader to imagine modes of existence beyond the simple chronologies humans are taught to embrace.
Read the quotes below and think about how they relate to Sum. If you're feeling ambitious, read one or both of the books and contemplate how Sum builds on their themes.
"Suppose time is a circle, bending back on itself," Lightman wrote in the opening chapter of Einstein's Dreams. "The world repeats itself, precisely, endlessly."
"From my words you will have reached the conclusion that the real Berenice is a temporal succession of different cities, alternately just and unjust," Calvino wrote toward the end of Invisible Cities. "But what I wanted to warn you about is something else: all the future Berenices are already present in this instant, wrapped one within the other, confined, crammed, inextricable."
See how Sum, in turn, has inspired other artworks: