How did Geoffrey Chaucer use Giovanni Boccaccio’s Il filostrato?

Geoffrey Chaucer used Giovanni Boccaccio’s Il filostrato as the primary source for the plot of his own tragic verse romance, Troilus and Criseyde, composed in the 1380s.123

While Boccaccio’s poem provided the narrative framework—the story of the Trojan prince Troilus and his love for the faithless Criseyde—Chaucer significantly expanded upon the material. He infused the work with pervasive philosophical themes, particularly incorporating Boethian discussions regarding free will, determinism, and the nature of fortune.143

Furthermore, Chaucer’s adaptation is noted for its leisurely pace, deep introspection, and psychological insight, which dominate many sections of the poem. Unlike Boccaccio, who focused more on stories as pieces of action, Chaucer utilized the narrator’s direct commentary to control the emotional tone and sympathy for the characters, ultimately contrasting the folly of worldly sexual love with the eternal love of God.135