Every person is a balance of emotions and logic.

Sherlock Holmes is logical reasoning personified, but even he is susceptible to the influence of his own emotions. While many people are first attracted to looks and personality, Holmes is attracted to Irene Adler solely because of her extraordinary intellect and ability to outsmart him. Adler is also quite beautiful, but her looks appear secondary to Holmes, if they matter to him at all. At the beginning of the story, Holmes is understandably excited about the prospect of a big financial payout for taking the case from a member of the nobility. By the end, Holmes’s decision to be paid with a picture of Adler, rather than a priceless ring, reveals that what he values has shifted. Adler has compromised the rationality he relies on and prizes so highly. It is logical to want a financial reward for completed work; it is illogical to trade untold riches for a simple photograph. Choosing the photograph is an emotion-based decision and the antithesis of what Holmes purports to esteem. Although Holmes shows no interest in finding any sort of companionship, his fascination with Irene Adler proves that even the most logical person is not immune to emotions and can be rendered illogical, in the right circumstances.

Everything is not what it seems.

Many people in the story are dressed up in some kind of costume or disguise, from the King of Bohemia in a mask and ostentatious clothing to Holmes himself pretending to be a horse groomer. In fact, Holmes’s groom costume—meant to fool the other grooms into divulging information—is so convincing that even Watson doesn't recognize him at first. Holmes later dresses as a clergyman while he is lying and manipulating Adler into giving away the location of the photographs. Watson claims that Holmes transformed his very soul for this costume. Ironically, Holmes may be wearing the clothes of a holy man, but he nonetheless lies to get what he wants, yet another reminder that things are not what they first seem to be. After the “fire” in Adler’s home, Holmes believes he has outsmarted her, but instead, she ends up surprising him, subverting the expectation that Holmes is infallible. He does not recognize Adler's costume as she listens to him brag about catching her, and she leaves town before he can confront her. All of the masks, disguises, and lies serve as examples of the power of deception. Additionally, the success with which Holmes, Adler, and the King are able disguise themselves indicates their individual levels of adaptability and intelligence. The King of Bohemia fails to fool Holmes, which implies he is not as intelligent as Holmes and Adler, both of whom succeed in fooling other people.

Women shouldn't be underestimated.

Most of the story consists of men such as the King of Bohemia and Holmes underestimating Irene Adler and discussing how they will outwit her, but in the end, they are all surprised when a woman—“the woman,” according to Holmes—outsmarts them. From the start, Adler’s intellectual prowess is evident in the way she manages to gain an advantage over everyone she meets. She is cunning enough to get a king to fall in love with her despite the fact that she herself is not of the nobility, and the King’s revelation that he would have married her instead of his fiancée had she been from a higher social class illustrates that she continues to hold emotional power over him even though she was previously blackmailing him. Further, Adler is clever enough to resist any and all attempts to retrieve the photos; she keeps them hidden and refuses all bribes. Finally, she comes out on top in a battle of wits with the most renowned detective in England. The letter at the end of the story features an explanation from Adler as to how she managed to fool Holmes, which parallels the way Holmes often relays his thoughts to Watson at the end of a case. The letter makes it clear that Adler's thinking is so advanced that even the great Sherlock Holmes requires an explanation as to how events unfolded as they did, effectively flipping the script and placing Holmes in a position to be awed at someone else’s prowess.