A long time dispute among scholars has been the moral status of revenge. Because revenge is the most obvious theme of the play, a lot of debate has been made over it. One can make judgments on the morality of Hieronimo based on his revenge-focused goals but the question many scholars face is whether the fault of his intentions is truly his. Steven Justice theorises that the judgment of the play falls less on Hieronimo than on a society in which the tragedy results from a way of life. It is argued that Kyd used the revenge tragedy to give body to popular images of Catholic Spain. Kyd tries to make Spain the villain in that he shows how the Spanish court gives Hieronimo no acceptable choice. The court turns Hieronimo to revenge in pursuit of justice, when in reality it is quite different.
Some critics claim that Hieronimo’s attitude is what central Christian tradition calls the Old Law, the Biblical notion of an “eye for an eye”. Hieronimo’s passion for justice in society is revealed when he says, “For blood with blood shall, while I sit as judge, / Be satisfied, and the law discharg’d” (III.vi.35–36).
The nature of murder and death, performed and as natural phenomena, is also questioned. Smith considers the decade of the play relevant to the use of hangings, murders, and near deaths throughout the play. Multiple characters are killed or nearly killed throughout the play. Horatio is hanged, Pedringano is hanged, Alexandro is nearly burnt at the stake, and Villuppo is assumed tortured and hanged. Kyd consistently refers to mutilation, torture, and death, beginning early in the play when the ghost of Don Andrea describes his stay in the underworld: “And murderers groan with never killing wounds, / And perjured wights scalded in boiling lead, / And all foul sins with torments overwhelmed” (I.i.68–70). He vividly describes in these lines as well as others the frequency of murder and torture in the underworld. Murder and death make up the tragedy theme that holds true through the last scene of the play.
The central theme is essentially revenge. The given title explains that there is some sort of harm that has been put on the main character to make him want to seek revenge. Revenge, however, is not the only theme. One key theme is that of Wealth and Power. This theme is clear in the sole actions of Balthazar. He kills Horatio in the beginning to gain power that in turn gives him wealth. This is also clear with the character of Lorenzo. Toward the end of the play he tries to convince the king to get rid of Hieronimo. Lorenzo knows that in the absence of Hieronimo, he will become more powerful and closer to the king.
The play also has a theme of revenge in historical context. The play in a way re-enacts the conflict between Spain and England. Kyd takes this opportunity to patronise the Spanish Armada and to make a political joke. This is very popular in Elizabethan and Greek tragedies. The play is used as a sort of defence mechanism for the English.