Spock is sitting alone in his room with the lights off. Emo much?
Kirk and Bones enter and turn on the lights. Spock says that the Vulcan looks like someone from his childhood—a "young student" with "great intelligence" and even greater ambition.
This student was a "revolutionary" because he turned to his "animal passions" instead of his "logical" Vulcan upbringing. To him, emotions were the key to self-knowledge. This attitude led to his banishment.
Before Spock can finish his story, however, the three crew members receive a message and head to the bridge.