Enlightenment ideas of utilitarianism and rationalism, and suggested that prisons should simply be used as a more effective substitute for public corporal punishments such as whipping, hanging, etc. This theory, often referred to as deterrence, claims that the primary purpose of prisons is to be so harsh and terrifying that they deter people from committing crime out of fear of going to prison. The second theory, which saw prisons as a form of rehabilitation or moral reform, was based on religious ideas that equated crime with sin, and saw prisons as a place to instruct prisoners in Christian morality, obedience and proper behavior. These later reformers believed that prisons could be constructed as humane institutions of moral instruction, and that prisoners' behavior could be "corrected" so that when they were released, they would be model members of society.