The threshold between dreams and realities has been an eternal source of fascination to both readers and writers ever since the beginning of literature. One of the most compelling devices to complete this is the protagonist, who can only dream in reality and experience reality in his dreams. This concept merges surrealism, psychological twist, and existential questioning to delve into perception, identity, and the subconscious mind. If done perfectly, it can create a different sense of storytelling and raise issues of what can be real and what can be imagined. Writers who engage with this concept often place themselves in the shoes of their protagonists, allowing both a mental and philosophical, even personal discussion about the boundaries between dreams and realities. For writers, this is pushing the barriers of confronting storytelling and exploring the labyrinth of human minds.

The notion of a character lost in dreams and reality has been used by some of the greatest literary minds. One of the earliest and most famous instances is Don Quixote by Miguel de Cervantes. Although the novel predates modern psychological theories of dreams, the author is one of the first to propose a character who begins to believe in the reality of his imaginary world more than the material one. Quixote's dreams of knighthood and adventure often blur the line between reality and fantasy in a tragi-comedic manner that reveals the depths of a delusion.

Alternatively, in The Metamorphosis, Franz Kafka speaks through the transformation of Gregor Samsa into a massive insect, serving as a metaphor for the disorienting experience of reality as a dream. This novel unfolds in a nightmarish context, reflecting the confusion faced by those who feel they are living a life disconnected from what they believe to be real. In more recent works, authors use this theme but often with more explicit psychological or abstract considerations. For example, in the Matrix trilogy, or in Christopher Nolan's film Inception, where the mind builds up complex layers of dreams within dreams, and the characters struggle to find out on what level of existence they are operating, Dom Cobb must grapple with his memories and regrets while trying to determine whether the reality in which he lives is merely a dream. This multi-leveled reality creates a world in which the boundary between waking life and the subconscious becomes nearly impossible to perceive, encouraging the audience not only to question what is real but also what being human means.

The difficulty here for authors wishing to use this method in their writing is to build a seamless connection between the world of dreams and that of reality. The trick is to embody the protagonist's struggle between reality and dreams into the pattern of his or her emotional journey. This technique can symbolize personality crises, mental instability, or a more philosophical insight into the nature of existence.

Authors could also play with narrative structures to produce a sense of disorientation, where they alternate between dreams and scenes from waking life to reflect the instability felt by the characters. Writers could likewise turn to devices like unreliable narration or changes in perspective to explore the protagonist's hold on reality. Dream logic, surreal imagery, and a fluid conception of time can capture the feeling of being stuck in an endless loop of questioning what is real. Such storytelling, if done well, can invite uncertainty and reflection in the reader, asking them to confront their idea of reality and identity. In addition, this creates an opportunity for the author to play with nonlinear storytelling and fragmented structures, moving in and out of time, memory, and perception.

In conclusion, the shift to characters existing only in dreams has influenced writers across generations. This device enables the exploration of human consciousness, identity, and the boundary between reality and imagination. When done well, such stories remind the readers to reflect on their idea of reality and their place in the vast universe.