In W. Somerset Maugham's novel "The Moon and Sixpence," the phrase "Impropriety is the soul of wit" suggests that humor often arises from breaking societal norms. Maugham explores the concept that true cleverness and insight can be found in the unorthodox or unexpected, challenging conventional standards of behavior and thought. This idea reflects the protagonist's journey as he navigates a world that often constrains creativity with rigid expectations.

The novel highlights the tension between artistic ambition and social convention, illustrating how the characters grapple with their desires and the limitations imposed by society. Maugham's work celebrates the power of wit and the freedom that comes from embracing one's individuality, even if it means stepping into the realm of impropriety. Ultimately, this theme encourages readers to question the status quo and recognize the value in thought that defies conventional wisdom.