One of the most important realizations that Montag makes is that he is capable of change. At the outset of the novel, Montag appropriates reality through the lens of obedience and stasis. Yet, as his characterization progresses, he learns more about who he is and his capacity for change. He begins to understand that he is able to actively construct a world for himself where change is evident. Montag makes the realization that he can be an agent of change.
Another lesson that Montag learns is that what he accepted as truth is actually deception. His role as a fireman was not to perpetuate anything constructive, as Beatty would have him believe. Rather, it was a force of negation, something that Montag comes to realize over the course of the narrative. Montag also learns that Mildred is not content with her being. She is actually quite miserable and that her attempts at suicide are calls to illuminate such a condition. Montag also learns that what was once constructed he is a part of the false world and to discover truth, he must make great sacrifices to both his life and way of thinking. Embracing books and reading becomes a part of such a dangerous mission that he once would not have envisioned himself undertaking. These become valuable lessons that help to define the arc of his characterization.