It is difficult to go very far in analyzing themes from The Fault in Our Stars without identifying the theme of love. Love is a dominant theme in the novel. It is experienced on different levels with different characters. The love of another, the love of self, the love of life itself are all examples of how the theme of love is evident in the story. Love is shown to be the force of redemption and restoration in a world that is filled with decay. In order to offset the transient and fleeting nature that life is shown to be, love is a universal force, almost defying temporality. This becomes evident when Augustus reveals to Hazel his love for her:
I'm in love with you, and I'm not in the business of denying myself the simple pleasure of saying true things. I'm in love with you, and I know that love is just a shout into the void, and that oblivion is inevitable, and that we're all doomed and that there will come a day when all our labor has been returned to dust, and I know the sun will swallow the only earth we'll ever have, and I am in love with you.
The theme which explores the redemptive powers of love can be seen in the imagery that Augustus uses to articulate his emotions towards Hazel. Love is cast against images of decay such as "the void" and an "oblivion" being "inevitable." In contrast to the condition of dust and the truth that "the sun will swallow the only earth we'll ever have," love is shown to be a universal force. The theme of love is bound throughout the novel's narratives.
Another theme that is displayed throughout the novel is the power of human action. Human agency is depicted as a force that exists despite the world around the individual. In contrast to a "winter" of one's existence and a setting in which the forces of nature seem to be dominant in determining life and death, human beings are shown to possess the capacity to exert freedom. Even in the most dire of conditions, individuals are active agents of their own action. Hazel and Augustus represent this. They love one another, despite how there is the unavoidable condition of death and decay that surrounds them. They have the power to choose life in going to Amsterdam, in rejecting what others, namely adults, say, and in loving one another. They choose agency in the face of realities that often silence choice and voice. Neither of them accept a fated condition of being in the world. There is a noticeable absence of silenced voices, showing that human choices can even transcend death and dying. The ending idea of the novel reflects this: "You don't get to choose if you get hurt in this world...but you do have some say in who hurts you. I like my choices.” Augustus's assessment of what it means to live in the modern setting is one predicated upon choice and being content with the decisions made. In this vision of consciousness, external forces do not impinge on the individual's ability to take action. The theme of human choice is a critical one in the novel, and is an embedded part of both characters' narratives.
Finally, I would suggest that there is a theme of transformation which is present in the novel. At the first encounter, Hazel speaks about her condition and Augustus replies with the idea of how transformation is a part of the human condition:
Don’t tell me you’re one of those people who becomes their disease. I know so many people like that. It’s disheartening. Like, cancer is in the growth business, right? The taking-people-over business. But surely you haven’t let it succeed prematurely.
Augustus speaks to the idea that human beings can transform their identity and be more than what they are defined by external reality. In refusing to "become their disease," Augustus and Hazel reflect how human transformation is evident even when life might be fleeting. Augustus's quote reflects the theme that human beings can change and represent transformative figures. They do not need to succumb to the "taking- people- over business." Human beings do not have to take the form of the world around them. Rather, they can be transformative in the face of such reality. In this regard, the novel's theme of human transformation is seen in different settings. Hazel transforms as a result of her love for Augustus, who also transforms because of the feelings he has for Hazel. Van Houten's failure to prevent death and sadness from overtaking his own life is a critical example of how not to live, something that Hazel and Augustus internalize in their own lives. The ability for human beings to transform is a critical theme in the novel. It is shown to be an almost absolute necessity in counteracting the world in which individuals live. It is one where fault might very well rest "in our stars," but one that does not have to prevent human change and transformation.