What are the purposes of criminal punishment? Four that are mentioned often are the following:
1. Retribution – imposing a punishment on someone who deserves it because of criminal behavior; the punishment must be just, i.e., proportionate to the gravity of the crime (neither excessive nor deficient); the more serious the crime, the more severe the punishment, and vice-versa. (Aristotle is a retributivist.)
2. Deterrence – punishment aimed at prevention of crime. There are two types of deterrence: general and special. General deterrence is where we punish A in order to send a message to B: “Don’t do what A did, or you might receive this punishment.” Special deterrence is where we punish A in order to get A to “sin no more.” Most debates about deterrence center on general deterrence.
3. Reform of criminals (“rehabilitation”) – the idea that punishment can be used as a method of “re-grooving” criminals (via psychotherapy, job training, education, etc.) so that they can be brought to function as productive members of society.
4. Protection of society against criminals by way of incapacitation. If a criminal is imprisoned or executed, society is protected against the criminal.
Three of these theories are applicable to the death penalty. (1) The death penalty is a form of retribution as long as it is deserved by the criminal. The death penalty should be imposed only on those who deserve it. Are there any crimes that are so bad that the perpetrators thereof deserve to be executed? If so, then the death penalty is justified on retributivist grounds.
(2) Whether the death penalty has a significant general deterrent effect or not is very much argued about. Even the “experts” disagree about that. However, if you subscribe to the deterrence theory of punishment, and if it could be proved that the death penalty achieves a significant level of general deterrence, then you would have to support the death penalty.
There is no doubt that the death penalty has a *special* deterrent effect: If we execute A, he will not commit further crimes, nor will he do anything else (in this world). He will be dead.
(4) The death penalty obviously protects society against any criminal who is executed. So it can serve this purpose.
(3) The death penalty does not serve the purpose of reforming or rehabilitating the criminal. It results in his death.
If you want to develop a consistent and adequate point of view on the death penalty, you must take these various theories of punishment into account, and you must not get hung up on any one angle on the subject. Above all, your thinking should not be based just on feeling or emotion. In philosophy, we try to base our views on logic and reason.
Just something to think about. (Once in a while, we succeed.)