The sentence that helps the reader determine the theme is: "He experienced shock at certain moments in his life, and it pleased him."
This sentence highlights the theme of the story, which is the importance of embracing uncertainty and the element of surprise in life. The boy initially enjoys the power of seeing the future and using it to his advantage in various aspects of his life. However, he eventually realizes that this ability robs him of the excitement and unpredictability that makes life meaningful. By choosing to stop using his powers and experiencing shock in certain moments, he finds joy and satisfaction.
This sentence emphasizes the boy's change of perspective and his realization that the absence of surprises makes life less fulfilling. It conveys the message that life's surprises and uncertainties are what make it truly worthwhile and enjoyable.
Overall, this sentence helps the reader understand the underlying theme of the story by explicitly stating the boy's satisfaction with experiencing shock and reinforcing the idea that embracing uncertainty leads to a more fulfilling life.