But as Van casually directed the searchlight of backthought 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.
In the narrative, Van reflects on his past, traversing a complex mental landscape where memories intersect and diverge, akin to paths highlighted by a searchlight. This introspective journey leads him to contemplate profound concepts regarding the relationship between space and time. He appreciates how these elements not only coexist but also influence one another, revealing the intricate nature of human thought and perception that would preoccupy him later in life.
As he navigates this intellectual labyrinth, Van begins to confront deeper philosophical questions that question reality's very essence. The notion that his existence is intertwined with mortality encapsulates the poignant realization that life is finite; understanding one’s being is tied to the inevitability of death. This dense and contemplative insight captures the essence of Nabokov's exploration of existence, memory, and the intertwining of time and space.