Mrs. Putnam has been made desperate by the deaths of her seven babies, and, now, her sole living child has been growing unwell. She is panicked by the thought that she could lose her one daughter, and she needs to find a reason for her losses; she needs there to be a reason.
When Rebecca Nurse advises the Putnams to rely on the doctor and prayer and suggests that, if they want to find fault, "Let us rather blame ourselves [...]." Such a suggestion could imply that the Putnams themselves could somehow be at fault for their terrible misfortune -- at least, that's how Mrs. Putnam takes it -- and the Putnams become very defensive. Mrs. Putnam complains that Rebecca has never lost a child or even a grandchild and she, herself, has only one child left. Mrs. Putnam cannot fathom why she has been subject to such awful losses and Rebecca has not, and she needs there to be a reason. It seems that she cannot bear the possibility or suggestion that she has done something to warrant or deserve this lot. She is a good, pious woman, just like Rebecca (in her mind); why would God punish her? It doesn't make sense to Mrs. Putnam, but what does make sense is the possibility that someone evil has inflicted these tragedies on her. It is easier to place the blame on someone else rather than to accept that it is just bad luck (which the Puritans didn't really believe in anyway) or something, somehow worse.
Ann Putnam has sent her daughter Ruth to get Tituba to conjure the spirits of her seven dead babies. Tituba, a slave from Barbados, conducts island rituals, but it seems Ann Putnam must believe these rituals can reveal truth. Ironically she is one of the first to call Tituba a witch.
She questions how others like Rebecca Nurse can have so many healthy children while she has only one, having lost seven at birth. Goody Putnam holds the midwives responsible for the babies' deaths, and in her twisted mind, she condemns them as witches. Although we can feel sympathize with her loss of apparently healthy babies, we are distressed that the warped logic she uses ensnares innocent people. The Puritans' understanding of science was primitive by today's standards so they had few ways of determining why some events happened, such as the babies' deaths. Ann Putnam and her husband are eager to blame others for their complaints.