Geoffrey Chaucer is considered one of the Fathers of the English Language and Literature.
one of the reason is that he decided to write his masterpiece, The Canterbury Tales, in Middle English, but we can consider many other aspects that were completely innovative during the 14th century.
From a literary point of view, it's important to remember that Chaucer (after meeting Boccaccio and Petrarca in Italy) was the first writer who took Renaissance to England.
From a social point of view, he comoletely shattered the feudal hierarchical system, describing a new medieval England. His irony and his psychological study of the characters who embodied several social classes of the time, represent a proper satire of his world and an interesting mirror of society and of human nature.