Conformity and individuality are at the heart of this play.
The play speaks to anyone who has lived in a society where the questioning of authority and of the general opinion leads to rejection and punishment.
John Proctor and Giles Corey stand as examples of inviduals who maintain their independence and question the authority of the court in Salem, while much of the town succumbs to the pressure to conform.
The specific pressures set against Proctor and Giles are directly related to conformity as are the accusations used against them.
In court, Proctor's choice to avoid baptizing his child in the church is used as evidence against him. This is, on the simplest level, a symptom of Proctor's choice to remain an independent individual. He refuses to conform for the sake of appearances. He has his own opinions and his own reasons for doing or not doing things. In the case of the baptism, Proctor does not want Reverend Parris to touch his children and so chooses to avoid the rite of baptism.
Proctor's earlier resistance to the town's authority makes him a suspect when he faces the court and accuses it of false deeds. He will not bow to Danforth or to Parris. He stands as an individual set against the will of the group.
He is dangerous to the proceedings precisely because he does not believe in them.
After his arrest, Proctor is tempted to conform. He is presented with the option of saving his life by betraying his principles and signing a false confession. This confession is, essentially, a means to remove Proctor's individuality and independence and to subordinate him to the power of the group.
Like Giles Corey, Proctor finally refuses to be reduced by the community's impulse toward enforced conformity. Individuality should be honored, in part, because it can be trusted. The group, however, is possessed of a moral bankruptsy, comprised of people who have abdicated moral judgement in favor of conformity. This is a dangerous quality, as the play makes clear.
Miller demonstrates how peer pressure can lead individuals into taking part in actions which they know are wrong.