Geoffrey Chaucer (ˈtʃɔːsər; c. 1343 – 25 October 1400), known as the Father of English literature, is widely considered the greatest English poet of the Middle Ages. He was the first poet to be buried in Poets' Corner of Westminster Abbey. While he achieved fame during his lifetime as an author, philosopher, and astronomer, composing a scientific treatise on the astrolabe for his ten-year-old son Lewis, Chaucer also maintained an active career in the civil service as a bureaucrat, courtier and diplomat. Among his many works are The Book of the Duchess, The House of Fame, The Legend of Good Women and Troilus and Criseyde. He is best known today for The Canterbury Tales. Chaucer's work was crucial in legitimising the literary use of the Middle English vernacular at a time when the dominant literary languages in England were French and Latin.