Honor
Honor is the play's central theme, but it is and abstract concept that is interpreted and exhibited differently by various characters. Hotspur, for example, is considered the embodiment of honor for his military prowess and dedication, while Prince Harry is often criticized as a the embodiment of dishonor for choosing debauchery over his royal obligations. Furthermore, while the play suggests that honor is something inherent to a strong leader, it also criticizes those who would pervert the concept of honor for their own means – that is, those who use the term as a way to portray warfare as anything other than brutal, violent, and devastating.
Kingship and Power
Of course, one of the themes directly related to that of honor is the notion of kingship, power, and legitimacy. As many of Shakespeare's history plays do, 1 Henry IV interrogates what it means to be a strong and successful leader. It also, however, questions the notion of kingship as slippery in terms of legitimacy: King Henry IV usurped the crown from someone else rather than inheriting it, which immediately casts doubt on his position among the rebelling characters. The play therefore poses the question of how subjects are to respond to a king's rule, and what power may lie with the people if kingship is disputed.
Language and Communication
The plays of the Henriad (Richard II, 1 Henry IV, 2 Henry IV, and Henry V), are famous for their portrayal of both noblemen and commoners throughout. Moreover, this diverse cast of characters also features a number of languages and dialects besides standard English, including Irish, Scottish, Welsh, and, in the case of Henry V, French. Most agree that the incorporation of these languages contributes some levity to an otherwise serious play, as characters speaking different languages have a difficult time understanding one another and frequently misinterpret what is being said. However, this varied communication in the play also contributes to the notion that, at this point in English history, England was itself becoming a diversified state of language and culture. In many ways, the diverse communication in 1 Henry IV helps set the stage for the epic transformation of Prince Harry, who rules with a surprisingly democratic fervor in Henry V.
Gender
Gender in 1 Henry IV is significant largely because of the absence of women: in a play concerned with honor, courage, warfare, and power, the plot focuses on relationships between and among men while almost entirely excluding women from significant events. In fact, that the male characters are so focused on maintaining their honorable reputations (gained almost exclusively through military prowess), suggests that women, marriage, and the domestic sphere are actually threats to this pursuit that can "soften" or "weaken" an otherwise valiant man.
Family
Family dynamics – specifically father-son relationships – are intimately entwined with the themes of power and order in the play. Of course, the most notable example is the tension between King Henry IV and his son, Prince Harry, who have a strained and contentious relationship due to Harry's predilection for debauchery rather than princely duty. Some have even noted that Falstaff – Harry's companion in pranks, jests, and other antics – becomes a type of surrogate father for Harry in a way that King Henry IV cannot fulfill, due to his role as "father" to the state of England. In many ways, the tense relationship between the king and the prince parallels the rebellion taking place throughout the play.
War and Rebellion
War serves as the backdrop of the entire play. Indeed, the play begins and ends with scenes of warfare, with the promise of more battles in the sequel, 2 Henry IV. Different characters have different perceptions of war's utility and its role in maintaining a prosperous state. Hotspur, for example, sees war as the ultimate embodiment of masculinity, where one might prove his courage and gain accolades and power from his martial success. For Prince Harry, war is a site of redemption and transformation, where he abandons his past antics and exhibits the initial attributes of a strong ruler. Finally, Falstaff provides the most controversial perspective of war in the play, as he suggests that the romanticization of the battlefield is nothing more than a hollow attempt to beautify what is fundamentally gruesome and destructive.
Order
In a play dedicated to dramatizing rebellions, the theme of order and rules is intimately linked to the themes of power and family. The play depicts two central "rebellions" in its plot: first, the youthful rebellion of Prince Hal against his father and his royal duty, and second, the rebellion of the Percys against King Henry IV. Notably, both of these "rebellions" threaten the order of the English state (as Prince Hal is set to inherit the throne), and the play questions the extent to which either of these rebellions are justified. In the end, both rebellions are ultimately squashed on the battlefield, as Henry defeats Hotspur and Hal steps into his role as soldier in his father's army – and order is (temporarily) restored to England. Of course, the play implies that more unrest is to come in the sequel, showcasing the difficulty monarchs faced in maintaining a stable state.
