First of all, and before we go into the thematic issues that concern us above all, thinking about these lines will give us an opportunity to look at the innovations in poetic style that characterize Chaucer's poetry. For Chaucer brings such important devices as end-rhyme and regular metrical rhythm into English verse. Thus, the lines are in iambic pentameter, which means that they consist of five rhythmic units or "feet" and that each foot is composed of first an unstressed and then a stressed syllable. Chaucer brought these sophisticated poetic techniques to England from both his wide reading in different languages (particularly in French and Italian) and from his travels on the European continent.
Looking at the lines you will notice that the words rhyme at the end of the line and I hope you will have an opportunity at some point to listen to a reading of Middle English when you will hear that on the whole an Iambic Pentameter rhythm is followed. (It is difficult to reproduce this for you on-line, to give you an idea of how Middle English actually sounds, particularly when the e's at the end of words are stressed in Middle English, though not in Modern English.)
Turning now to the themes of The General Prologue, to the co-presence of Realism and Romance within it, we begin by taking note of the place and time at the beginning of the story, the temporal and geographical conditions of the narrative's inception.
If the place is the road between the great city of London and Canterbury, the sacred Cathedral town of the Christian martyr, Thomas á Becket, the time is April, the month most associated with spring. It is in his beautiful description of spring that the narrator of the poem, a jolly and friendly yet deeply ironic fellow whom we'll call "The Pilgrim-Chaucer," shows his ability to be both idealistic and realistic in his depiction of his fellow human beings. The Pilgrimage is meant to be the journey to a holy place where the soul may renew itself (this being a kind of high Christian romance, the quest of the human spirit for higher meaning). The language of the Pilgrim-Chaucer, the narrator of the prologue, takes, however, a complicated tone. Showing that the Pilgrims go to Canterbury for all the wrong reasons, he manages to be at the same time ironic about human limitations and sympathetic about human necessities.
What he is saying if we read the lines carefully is that men and women go on a spiritual pilgrimage for natural reasons, they travel because the thought of a journey appeals to their physical beings. When the Pilgrim-Chaucer describes their reasons for traveling, "that nature pricks their hearts," (l. 11), we are reminded that according to strict Christian orthodoxy man is meant to be a creature of spirit not nature. Yet we cannot see the narrator as an austere moralist. The Pilgrim-Chaucer who creates an atmosphere of charming playfulness with his descriptions of joyous spring and the gay life of nature, when "smalen fowles maken melodye" (l. 9 ), is not likely to condemn people who are moved to action by such scenes.
Chaucer wants to say is that people are more natural than spiritual but, judging by the Prologue as a whole, unless they become positively corrupt, he seems to believe they can be forgiven for their human, very human, natures. Nevertheless, our seemingly naive but actually quite shrewd narrator, our friend "the Pilgrim-Chaucer," ends his introductory description (these lines which place the setting of the narrative) with an ironic comment. He mentions that people go to bless a holy man "That hem hath holpen whan that they were seke" (l. 18), that is, "who had helped them when they were sick."
Yet thanking God for his conferred favors surely ranks as a comparatively low level of spirituality. Such pilgrims look to God out of self-interest, thank Him for what he has God done for them instead of thinking about what they can do for God. Perhaps the Christian idealism of the poem would condemn most of the pilgrims. Yet this insight into our (very) human nature also suggests a certain honest and humorous realism about people. Not as devoted as they might be, many, if not most, people may be forgiven in the end.
Thereafter, from ll. 19-42 friendly The Pilgrim-Chaucer tells you about his plan for the narrative, his intention to describe each of the pilgrims. We see that he's a very friendly man who seems almost superficial in his readiness to be friends with everyone and assume that he understands them all. Yet there's a shrewd man underneath the apparent easy-going fellow. Though he may seem too easy-going to be wise, there is hidden wisdom in him, and I believe he is a reliable narrator after all, one whom we can trust, and one who speaks with different levels of irony and seriousness.