What is a major theme of The Crucible, and how would audience members or readers recognize this theme in the play?

1.  While The Crucible, like most literary works, possesses several themes, you could make a strong argument that Miller's main subject in this masterpiece is power.  All the other themes in the play can be traced back to power, and the various conflicts present within the play arise because of characters' relationship with power/authority.  For example, the young Puritans girls (as history and Miller show) possessed no power.  They received no formal education, had no choice in their future, and gained very little positive attention from anyone.  Mary Warren, a servant to the Proctors, even has to obey John and Elizabeth as if they are her parents, and they have the authority to beat her (see Act 2). Many historians and Miller argue that the girls' false accusations and the resulting hysteria are a consequence of the girls' seeking attention and power. Similarly, landowners like the Putnams start to accuse other landowners of witchcraft so that they can gain their property and, thus, additional power. Finally, the judges--even after they know that the girls are lying--refuse to reverse their rulings because they do not want to hinder their authority.  This is why they see all questions to the court, such as Proctor, Nurse, and Corey's petition, as a threat to their power.

2.  In regards to readers interpreting or recognizing this theme, I think that it is most obvious in the judges' and Rev. Parris's conversations/actions and in the background notes that Miller provides before and throughout the play.