Ontology

Ontology is defined as the study of existence, or being. In East of Eden, Samuel exhibits an interest in ontology. It is not enough for him to simply exist, he has to understand. He is always looking for purpose and grand explanations for why we are. He is studying his very existence. 

Similarly, Holden Caulfield in The Catcher in the Rye exhibits a desire to give meanings to the world around him. He cant see a real reason as to why we exist, and throughout the entirety of the novel is studying himself and his existence on this earth. He wants more than to just exist, he wants to understand the purpose of human existence.