Why has Reverend Parris sent for a doctor as The Crucible begins?
Parris has a daughter, Betty, who has taken ill. She is unresponsive and silent though at times she seems to want to jump out the window.
It is not revealed whether her illness is feigned or if it is a genuine physical response to a traumatic situation, but it is clear that she is easily influenced and deeply affected by her experiences.
Betty's apparent illness is the surface reason that Parris has called for help. He is worried about his daughter's health, physical and mental.
There is more reason for Parris to worry, however, as he has seen his daughter dancing in the woods at night, an act that is taboo. The thought of witchcraft is one that seems to have occurred to Parris because he calls for Reverend Hale to come see Betty. Hale has a reputation for treating cases of witchcraft.
Reverend Parris is the community's spiritual leader. He is expected to keep his own home the most pure and holy. Because he himself discovered the girls dancing in the forest (and saw one naked), he fears that the community will rise up against him. "There is a faction that is sworn to drive me from my pulpit."
Although his niece, Abigail, has confessed to dancing and denied witchcraft as their motivation, calling it "sport," he suspects her of more. Her history of being released from the Proctor family's service causes him to fear her actions and the town's response.
Parris says he has called for Reverend Hale as "a precaution only."