In the scene when he get's threatened by the group of kids outside his Father's work, we see him reading the works of Plato. This scene cronologically speaking is not far after he finds out who he is. This shows that he is already questioning his existence and meaning by resulting to philosophial texts
Plato's main theory is the Cave, whereby a man escapes and see's an existence beyond the cave whereby everyone else lives and sees only shadows. Plato theorised that one has a moral obligation to show the people in the cave the outside world, however in the story he is killed by the cave people because of them not wanting to accept it.
How does this relate to Man of Steel? Clark is having an inner moral fight with himself as to whether show the people the truth about his existence and are we alone in the universe, and risk compromising the safety of himself and his family, or sticking with his Father's teachings and keeping it a secret.