In the context of law and prisons, incapacitation is one theory of why it is important to put people in prison. The idea behind the theory of incapacitation is that a person who is in prison no longer has the capacity to commit crimes. By putting the person in prison, we prevent them from committing further crimes.
There are two main reasons for putting people in prison. One of the reasons is punishment. Some people feel that a person who commits a crime deserves to be punished. Being put in prison and deprived of one’s liberty is a punishment. Therefore, it is proper to put people in prison if they commit crimes that are sufficiently serious.
By contrast, the theory of incapacitation does not rest on the idea of punishment or of giving people their just deserts. Instead, it focuses on keeping society safe. If a person is in prison, they will of course be unable to commit crimes against people outside of the prison. Therefore, when we put someone in prison, we are doing so to keep the rest of us safe, not to punish the person.
My own view is that more Americans believe in the idea of punishment than the idea of preventing people from committing further crimes. This is, for example, why we are willing to have people continue to serve time in prison long after they are too old to be likely to commit further crimes. It is also a major reason why many people support the death penalty rather than life in prison with no possibility of parole.
So, incapacitation is one theory of why we should put people in prison. It is based on the idea that a person in prison no longer has the capacity to commit crimes against those outside the prison.