Modern liberal Christians have an almost entirely negative view of punishment. They tell us regularly what punishment must not be, but have a very limited idea of what it should be.
Punishment must not be retaliatory or retributive, we are told. This is “punitive” or “mean-spirited”- a favorite phrase of blacks attacking longer sentences in the 1990’s. Punishment, as defined in the theory of operant conditioning by B.F. Skinner, is some action, either the imposition or removal of some condition, that reduces or eliminates a behavior of the organism. By this definition, incapacitation isn’t even punishment, since it is only intended to make the behavior impossible, rather than act on the nervous system of the subject to produce change.
In general, however, because while people are not particularly rational, they have fear of punishment so retaliatory or retributive punishments work well. God himself set out many retaliatory and retributive punishments in the Old Testament law, for the purpose of protecting people’s dignity and maintaining social cohesion.
The progressive Christian concept of punishment is more like a time-out for a small child- the offender has some time to calm down, collect himself and realize he has been bad. This should be as short as possible- seven years for first-degree murder, five years for other intentional homicides, three years for other violent crimes, less for non-violent crimes. As strange as it may seem, these were common sentences in the 60’s and 70’s.
Since elimination of witnesses makes conviction less likely, it was clearly a rational act from a punishment standpoint to kill robbery victims, and so murders during armed robberies were common.
Beyond having a brief period to collect himself, the offender could receive education and job training, thus gaining economic opportunity as an alternative to crime. This assumes that crime is a matter of want, rather than something else.