In Dialogo di Tristano e di un amico, the final dialogue of Giacomo Leopardi's second edition of the Operette morali (1834), the main character, Tristano, comments on how human beings in modernity value more the spirit over the body. Tristano's declaration formulates an important distinction found throughout Leopardi's works: human beings of antiquity were more concerned with the care of the physical body and human beings of modernity were more concerned with the care of the immaterial spirit. Leopardi uses the term "spiritualization" to describe human beings' increasing internalization, leading them to become physically weaker and spiritually stronger. Consequently, for Leopardi, spiritualization is one of the principal reasons for modern humanity's unhappiness. The process of spiritualization becomes the transitional factor from the age of antiquity to the age of modernity. To pinpoint the origin of spiritualization, Leopardi turns to literature, and establishes that Homer was the last poet of antiquity and all other poets after Homer were a part of modernity. Literature becomes Leopardi's medium through which he juxtaposes antiquity and modernity, as he contrasts the epic heroes of modernity and antiquity. He states that the heroes' virtues mirror their era's virtues. Hence, Tristano becomes the crowning example of the modern epic hero since his melancholic disposition mirrors the virtues and characteristics of the modern era. This thesis explores Leopardi's philosophical analysis on the body and the spirit to gain a better understanding of the concept of spiritualization, the origin of this concept, and its impact on human history. In addition, I analyze the Dialogo di Tristano e di un amico through the lens of spiritualization to reveal to readers the reasons for the poet's melancholic perspectives regarding human progress, the body and the spirit, and literary works and epic heroes in the modern age.