Betraying my Zen-flavored inclinations....
Trying to think one's way to enlightenment is like looking for the right wild fox to care for a henhouse.
The search for a mind-controlled enlightenment is most commonly limited by an underlying ego assumption that it's actually something that can be possessed.
how
>>> can we know that something is eternal?
Yes.
If, as according to Kagyu teaching, it is real. To be real, it must be unique, unconditioned, and unchanging.
Then we have to find it. Far easier said, than done. A lifetime of practice may not reveal such a thing, but it might.
The US prison system is awful. It is a breeder of injustice, gangs and cruel punishments. In Spain it seems we have a better system. Larry Lawton, ex-convict (11years in Federal institutions) agreed with this as well as mentioning how certain European countries are just so advanced in this aspect.
The problem of rapes for example...and gang violence/activity...
https://www.buddhistchannel.tv/index.php?id=9,3679,0,0,1,0
Here in an interview with Kobutsu Malone, revealing how this has not changed, perhaps it has even worsened:
" I actually got arrested in Washington, D.C., in 1968. I was at a friend’s house and was falsely charged with presence in an illegal establishment and possession of implements of a crime. I was sent to the D.C. jail. I stayed in there fourteen days, and on the second or third day I was in there I was beaten and raped. I managed to stick my foot in an electric gate and got transferred out to a hospital."
Such environments are cruel. I believe prison should be an isolated place for the benefit of society and the convicts, like an island where you can grow and heal, both you and society. But creating these pits of horror and torments, it seems like you are creating Hell on Earth for no reason. In the end, you just end up with more crime and damaged human beings.
Kotishka
I think a part of the view in Buddha's time has to do with the social system they were living in as well. It relied much more on the wisdom (or lack thereof) of those carrying out the sentence, was the guilty willing and capable of rehabilitation or would they only continue to commit harm? Versus the rules based systems (rule of law) that most of the world operates on today. While doing much to rectify and avoid the whims and abuses of the powerful at the time, it also has its downfalls, in that we're less able to rehabilitate and use good judgement to help those who are helpable.
person
Interesting how, while the Buddha accepts Angulimala and even the King too his transformation from a killer to a bhikkhu, Angulimala is still subject to the kamma of his criminal actions that inevitably lead to his gruesome death.
The Buddha says to him: "Bear with it, brahman! Bear with it! The fruit of the kamma that would have burned you in hell for many years, many hundreds of years, many thousands of years, you are now experiencing in the here-&-now!". Angulimala does not retaliate nor curse, he accepts it and thus released from samsara.
When I talk about providing sessions to prisoners, one important aspect is their acceptance of the deed they committed and the cost society has imposed on them: you murdered, you indeed did a wrong thing. But this should not become a source of eternal anguish or torment, you should ask for forgiveness and acceptance of your misdoing but also accept that the people you hurt might not forgive you and this is the result of your actions. What you do from now on is essential not only for your own well-being, but perhaps even for the well-being of others too.
Thanks for the sutta @Jason 
Kotishka
What you can truly know is what is being directly experienced in the moment. One of this is the experience of uncertainty!

The Buddha generally seemed to leave questions like this to civil authorities, and would likely be viewed as a consequence of their unskillful actions. There definitely does seem to be an acknowledgement of a person's capacity to change, though, and the Buddha accepted people who were murderers into the Sangha (e.g., Angulimala). So I think there's also room for things like restorative justice. But in general, long jail times for seriously violent crimes doesn't seem particularly anti-Buddhist in and of itself.
Jason
So, I haven't been up to date on this,but I just wanted to comment on how it's good you're trying to improve yourself. As with all things, it's a process and your desire to improve/change is competing with a host of other causes and conditions and habits, so it'll take time and effort, and will include successes and setbacks. I don't know know you personally, @marcitko, but I'm proud of you for the effort you're putting in and sharing it with us. Even if and when you fail, that effort is making you and the world better. Being self-reflective and forgiving is super important on this journey, which we're all on in some way, shape, and form, so try not to stop either, even when it seems difficult and pointless. Because it's definitely the former but certainly not the latter.
Jason
A refuge is a place of safety and calm. Whatever the external circumstances may be, a refuge provides us with all that we need to survive and flourish. The Buddha taught that the true refuge is internal and that it is something that we must create for ourselves. On one occasion, he listed ten virtues that contribute to the feeling of inner refuge:
1) Adopting appropriate boundaries for one's actions and speech.
2) Reading, studying widely and in depth.
3) Cultivating good, healthy relationships.
4) Being easy to speak to, open to feedback.
5) Finding ways and developing skills to contribute to the welfare of one's community.
6) Cultivating love for the Dhamma, finding joy in the teachings.
7) Making a steady effort to abandon the unwholesome and develop the wholesome. Diligent, brave, preserving and resilient in one's efforts.
8) Being at peace with and appreciative of the material supports one has acquired through honest endeavour.
9) Developing mindfulness. Knowing how to bear in mind, moment by moment, everything that is most relevant right now to growth in Dhamma.
10) Knowing how to think clearly, how to reflect, how to learn from experience. Seeing things in their true light.
Ajahn Jayasāro
11/7/23
Bunks