Final answer:
The phrase "Don't judge a book by its cover" advises against making judgments based solely on appearances. In 'Sir Gawain and the Green Knight,' characters often conceal their true intentions, prompting deeper understanding beyond first impressions.
Step-by-step explanation:
The phrase "Don't judge a book by its cover" means that one should not determine the value or character of something based entirely on its external appearance. In literature and life, this aphorism encourages looking beyond the superficial to understand true nature and substance.
In the story of Sir Gawain and the Green Knight, there are multiple instances where characters are not what they initially seem, which resonates with the idea of not judging too hastily. Sir Gawain himself, a knight of the Round Table, is tested for his chivalric virtues and finds himself in situations where appearances are deceptive. An example is the lord of the castle who is in fact the Green Knight, revealing that his intimidating exterior belies his noble intent to teach Gawain a lesson about humility and honor.
The characters in the story are seen to wear 'masks', with their true identities and intentions often veiled, which challenges both Gawain and the audience to look beyond appearances to discern truth and character.