We'll be honest with you, Shmoopers. This section is a bit tricky for The Maltese Falcon for a reason you might not initially suspect.
See, Spade searches a lot of pockets and a lot of apartments and uncovers a lot of things: an orchestra ticket for the Geary Theatre, leatherette cases, foreign coins, gold watches, colorful silk handkerchiefs perfumed with chypre (a fragrance known for its contrast between fresh citrus notes and woody oakmoss and musk accents). With this cornucopia of objects to choose from, you might assume that there'd be the same number of symbols, if we're thinking of a symbol as a physical object or character that represents an abstract idea.
But in The Maltese Falcon, most of these objects turn out to be completely meaningless. These physical things have no symbolic value because they merely serve as evidence for Spade to solve the crime. There's no hidden meaning in these objects, and they're important only insofar as they provide clues.
But notice that we said most of these things have no abstract meaning. There is one thing, and one thing only, in the novel that does function as a symbol. Guesses, anyone?
The Black Bird
If you said the falcon, then you've just won $1,000,000! The only symbol in The Maltese Falcon is the falcon itself, a statuette once given by the Knights of Rhodes to King Charles V of Spain. Gutman, Cairo, and Brigid O'Shaughnessy are driven by greed in their selfish pursuit of the black bird. They become so obsessed in their quest for fortune that they are willing to sacrifice anything to get it. In this sense, the falcon symbolizes the corrupting power of human greed and its pervasion through history.
Did the bird really exist? We're glad you asked (because we have told you anyway). The Maltese falcon dates back to the Knights Hospitaller, a religious order founded in the 11th century to provide care for poor and sick pilgrims to Jerusalem. In 1530, Emperor Charles V of Spain gave the Knights a large territory, including Malta (which is why they are also known as the Knights of Malta), in exchange for an annual fee of a single—live, not jeweled—Maltese falcon.
While coming up with the plot hook for The Maltese Falcon, Hammett became intrigued by what he called the "peculiar rental agreement" between Charles V and the Knights of Malta. The Crusades probably interested Hammett because of their mythic association with the Holy Grail, the cup Jesus drank from during the last supper. This link to the Crusades subtly elevates Spade to a knight on a noble quest.
But why a falcon? With so many birds of prey to choose from (snowy owl, hello?? We want our very own Hedwig, please), why all the fuss over falcons? Dating back thousands of years, falconry is the sport of training birds to hunt small prey. Well-trained birds were prized for their beauty, skill, and efficiency. Since the falcon is a fearless hunter, it has traditionally been a symbol of ruthlessness and prowess (sounds a bit like Sam Spade, no?).
But early Christians slightly altered the meaning of the falcon to reflect their own values. Instead of representing physical strength, wild falcons were seen as relentless killers and therefore became symbolic of evil, whereas tamed falcons represented Christian conversion and repentance. Coats of arms from the Middle Ages often featured falcons as a symbol of the pursuer, one who will not rest until his goal is achieved. This single-minded (almost blind) commitment to a single purpose should remind you of Spade and his fellow falcon-hunters.
Ultimately, the relentless quest in Maltese Falcon for the black bird ends in a wild-goose chase, bringing down the lives of all those who vainly pursue it. Greed destroys any chance for the characters to lead contented lives, yet they refuse to give up the chase. Even when Gutman realizes the bird is a fake, he vows to return to Egypt to pick up the trail again.
Of course, he gets killed before he can leave San Francisco, but his uncontrollable desire for the bird contaminates all his relationships with people (he was even willing to sacrifice Wilmer to the police). Hammett reverses the popular alchemic quest to turn lead into gold (by reducing the Maltese falcon from gold to lead).