Question: I saw this question somewhere in the Internet(I forgot the source) and I think this forum is a good place to ask it.

According to what I know, the atoms in a persons body are replaced every certain amount of years:
<https://skeptics.stackexchange.com/questions/18427/are-all-the-atoms-in-our-bodies-replaced-on-a-regular-basis>

Then, if a persons body atoms are replaced every x years, should the person be prosecuted today for a crime that he/she committed x years ago, when today that person is physically another person(different atoms)? 

And lets say hypothetically that 0.00001% of atoms are never replaced, should 0.99999% of the sentence in years be eliminated (the person is 0.00001% responsible for the crime) ?

This is a related question in the forum:
[Am I still the same person as I was yesterday?](https://philosophy.stackexchange.com/questions/2747/am-i-still-the-same-person-as-i-was-yesterday)

Answer: 
Arne Naess wrote many essays about the Self. In them, he argued for a concept called the Ecological Self, but along the way he used a series of phrases to challenge commonly held approaches to defining the self. Such class of phrase pairs looked like:

* I enjoy listening to Mozart.
* My body enjoys listening to Mozart.

Or

* I am my mother's son. ("daughter" if you are female)
* My body is my mother's son ("daughter" if you are female)

If one considers the pairs of phrases to not be *quite* identical, it suggests that "my body," i.e. the atoms in my body, are not quite exactly the same concept as "my self." Thus, replacement of the atoms in the body is probably not sufficient to be a change of self.
What is the purpose of punishment? If it is to link consequences to decisions, then the question is whether that old collection of molecules should have predicted the damage it would cause any better than this new collection of molecules.

Our notions of learning imply that behavior is a feedback loop and the consistency of personality is unrelated to the set of molecules that embody it, but related to the information that flows through them. So by and large, the prediction of recidivism remains good over long periods of time. Our morality gets no better with time, and the corresponding replacement of molecules, unless something else changes.

The better question is whether you should incarcerate, for instance, an amnesiac, or an addict who has just undergone something like ibogaine therapy, a rapist subject to chemical castration, or a terrorist who has undergone a religious conversion: a person who really feels like a 'new person' and has had a real part of their personality deactivated or removed in a way that has statistically proven likely to change current and future decision making.