Discuss the major theme in Sir Gawaine and the Green Knight?

One major theme in the story is chivalry....... the chivalry that is embraced and demonstrated by the Knights of the Round Table. Gawaine, the epitome of what makes a great knight is well known for his chivalry and morals. None-the-less, even Gawaine can be swayed by a pretty face..... chivalry forgotten and accompanied by major lapse in loyalty. Note, Gawaine never accepts the lady's offer of sexual favors, but he does accept a gift..... a a tunic with magical powers that will insure his life in the upcoming fight with the Green Knight...... a form of cheating, and an act that would be considered unknightly.