§ 29 Preventive Punishment
Punishment is in the second place preventive or disabling. Its primary and general purpose being to deter by fear, its secondary and special purpose is, wherever possible and expedient, to prevent a repetition of wrongdoing by the disablement of the offender. We hang murderers not merely that we may put into the hearts of others like them the fear of a like fate, but for the same reason for which we kill snakes, namely, because it is better for us that they should be out of the world than in it. A similar secondary purpose exists in such penalties as imprisonment, exile, and forfeiture of office.