Books
A chief event of life is the day in which we have encountered a mind that startled us.
— Ralph Waldo Emerson ‧ Essays, 'Character,' 1844

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The passage gives meeting a startling mind the importance of a major life event. Intellectual surprise becomes something worth remembering as a particular day. One reading values encounters that unsettle familiar ways of thinking, treating another person's mind as a powerful experience.
Context reviewed