LitCharts assigns a color and icon to each theme in The Sun is Also a Star, which you can use to track the themes throughout the work.
Immigration and the American Dream
Passion vs. Reason
Interconnectedness and Destiny
Isolation vs. Connection
Summary
Analysis
Four years ago, the conductor's wife announced that she didn't love him anymore. After the divorce, the conductor wondered what he could believe in if he couldn't believe in his own wedding vows. He kept the TV on but muted at night. One night, he saw a man addressing a room full of attentive people. The conductor unmuted the TV, and the next day, he researched Evangelical Christianity. It appealed to him, especially the parts about being born anew and sharing the gospel with others. This is why he spoke to his passengers. He feels pure joy in his belief that his life has meaning, and that God has a plan for him.
For the conductor, forming a connection with a higher power was a lifesaving change in his life—which he then attempts to pass on to his passengers.