The arrest of Rebecca Nurse, who is identified by Reverend Hale in the beginning of the story as having a reputation, far and wide, for being a most faithful and pious Puritan woman. Hale is awed to be in her presence.
The fact that she is accused of witchcraft, by Anne Putnam, who is merely exercising her anger and jealousy against Mrs. Nurse, because she has many children and grandchildren and Mrs. Putnam has lost all but one of hers, is a perfect example of how Miller expresses the hysteria of Salem blindfolding common sense.
The fact that Mrs. Nurse is put to death is an abomination of evil representing the extreme of irrationality in the play.
Miller is also a master at depicting irrationality being manipulated for the purposes of personal gain as well. The perfect example of this is when Thomas Putnam has his daughter Ruth accuse George Jacobs of sending his spirit out to assault her in her bedroom. Mr. Jacobs is the Putnams' neighbor who owns 600 acres next to theirs. He is an old man who walks with the aid of canes.
Thomas Putnam takes advantage of the irrationality of the hysteria of the witchcraft accusations to get rid of Jacobs so that he can acquire his land at a discount.
There are several examples of this in the play. The one that stands out the most in my mind is the reason behind why Martha Corey was arrested. She sold a pig to Walcott, that died shortly after he got it, because he wasn't feeding it properly. So, Marth chastised him, saying, "Walcott, if you haven't the wit to feed a pig properly, you'll not live to own many." Well, sure enough, his pigs keep dying. So, he supersitiously claims that the reason was because "Martha bewitch them with her books". The common-sense reason why the pigs are dying? He's starving them. The irrational, superstitious reason? Martha's a witch casting spells on them.
Another example is when Mary Warren casts the "final proof" that Sarah Osburn is a witch. After she turned her away from the house without food, Osburn mumbled and she "thought [her] guts would burst for two days after." The superstitious implication is that Osburn mumbled some sort of curse or witchcraft to make Mary sick. Never mind the logical answer which was that she just coincidentally happened to get some sort of bug.
Another example is when Cheever and Herrick immediately take the poppet situation as hard proof that Elizabeth is a witch, a superstitious belief, over the logical assumption that Abby saw Mary put the needle there and used the opportunity to her advantage.
These situations, and many others, show fear and superstitioun ruling Salem, not logic and reason.