Why did Dante Alighieri write De vulgari eloquentia in Latin?

Dante Alighieri wrote De vulgari eloquentia (c. 1304–1307) in Latin because, during the Middle Ages, Latin remained the standard medium for scholarly, philosophical, and political discourse. While Dante was a pioneer in using the vernacular for artistic prose, Latin was the traditional language used to address an educated, international audience on theoretical and doctrinal subjects.123

In De vulgari eloquentia, Dante provided the first theoretical discussion and definition of the Italian literary language. By choosing Latin for this specific work, he utilized the established academic language of his time to lend authority to his analysis of the vernacular. This practice was consistent with his other doctrinal writings, such as De monarchia, which also utilized Latin to expound on complex political theories.1