In Act I of "The Crucible," there is an assumption made that Betty and Ruth are sick due to bewitching or witchcraft. Even though the reader knows that Betty is pretending to be sick and refuses to open her eyes because she is afraid of what her father will do to her since he caught her and others in the woods the night before, dancing and conjuring spirits.
Reverend Parris does not believe Rebecca Nurse when she tells him that little Betty will wake up when she is good and ready, when she tires of playing her game. He is convinced, or rather wants an instant remedy, one that the local doctor cannot provide, so he turns to Reverend Hale of Beverly, once the doctor tells him that there is nothing physically wrong with Betty.
Reverend Parris's assumption that witchcraft is to blame for Betty's illness starts a process that is validated by the arrival of Reverend Hale who lends his credibility and authority on the subject to the situation in Salem.
Before the first act is finished, Abigail and the girls have decreed that witchcraft is afoot in Salem in the presence of Sarah Good and Goody Osburne. The hysteria feeds itself through the demands of the court for the names of others who were seen with the devil.
As the hysteria spreads, it takes on a life of its own, self justifying itself everytime another person is accused of witchcraft and with the confessions that emerge from innocent people who simply want to save their lives come the concrete proof that witches are, in fact walking around in Salem.
The town becomes consumed with the cry of witchcraft for different reasons. Some, like the Putnams see the opportunity to exploit or blame their neighbors for tragic circumstances beyond their control, such as when Anne Putnam accuses Rebecca Nurse of bewitching her seven babies who died at birth.
Or when Thomas Putnam has his daughter Ruth accuse Mr. Jacobs of witchcraft so that he can purchase his land, which is adjacent to the Putnams, as those accused have their property taken away and sold at a discount.
The whole town is consumed by the craze, the madness seeps into every home, even the Proctors, who try to stay out of the whole process. Even the finest citizens of Salem are not safe from the cry of the accuser.