Which novel is considered a significant work exploring existential themes?

The chosen answer is recognized for its deep exploration of existential themes through the experiences of its protagonist, Meursault. In Albert Camus's "The Stranger," the character's indifference to social norms and lack of conventional emotional responses illustrate existentialist ideas such as the absurdity of life and the search for meaning in a seemingly indifferent universe. The novel engages with the concept of existential freedom and the idea that individuals must create their own meaning in life.

In contrast, the other novels listed engage in different themes and styles, such as the struggles of adolescence and alienation in "The Catcher in the Rye," the critique of the American Dream in "The Great Gatsby," and the richly woven historical and philosophical layers in "The Name of the Rose." While all of these works are significant in their own rights, "The Stranger" stands out specifically for its alignment with existential philosophy, making it the most appropriate choice for this particular question.