But as Van casually directed the searchlight of back thought into that maze of the past where the mirror-lined narrow paths not only took different turns, but used different levels (as a mule-drawn cart passes under the arch of a viaduct along which a motor skims by), he found himself tackling, in still vague and idle fashion, the science that was to obsess his mature years - problems of space and time, space versus time, time-twisted space, space as time, time as space - and space breaking away from time, in the final tragic triumph of human cogitation: I am because I die.

Ada