Unlike most people in Salem, Rebecca Nurse is not prepared to attribute the various ills of daily life to witchcraft. Then again, that could be because Rebecca has been incredibly lucky in that she hasn't lost a single child or grandchild, something very rare indeed in those days.
In any case, the kindly, devout Rebecca believes that it's better for people to look to themselves for the causes of their troubles instead of going around looking for witches hiding in every nook and cranny.
The contrast with Ann Putnam could not be greater. Deranged by the loss of seven children, she's come to believe that there are dark, malevolent forces at work in Salem and that witchcraft is responsible for all her suffering. Instead of believing, like Rebecca Nurse, that it's better for people to look to themselves to find out what's causing all their troubles, Ann immediately cites witchcraft as the ultimate cause of all the wickedness that has made her life so miserable.
That being the case, she becomes one of the most enthusiastic supporters of the Salem witch trials, seeing it as an opportunity to drive out from the town the evil spirits that she believes killed her babies.
In going along with all this hysteria, Ann thinks she's doing God's bidding. Yet Rebecca also thinks she's staying true to her faith in insisting on a more rational explanation for Ann's misfortunes. This infuriates Ann, who seeks answers to her troubles in the realm of the supernatural.