They say that renters tend to trash things in ways that owners usually don’t, because they know that thing is not their own, so why bother? Well our very minds/bodies/lives are all leased, borrowed - nobody gets permanent ownership of these things.
Although it’s normal to have an inkling of concern for our future progeny, it’s a lot easier cognitively (for example) to rape and plunder the planet of its resources, knowing it won’t be our own problem to deal with. It’s easier to fuck someone over when you know you’re likely never to see them again.
So I want to imagine a world almost exactly like ours, except there are a fixed number of humans who can not die and can not reproduce. They can feel pain just as much as any of us, however, and this is important to note as this is not a consequence-free existence we’re talking about. We’ll suppose that these immortal humans have strong regenerative properties - so disease would still exist, but a disease which would normally be terminal would eventually run its course and disappear (though not without the same amount of pain as a mortal human would suffer from it). A person could be dismembered, incinerated, or even decapitated and eventually recover - but it would still hurt like a bitch. I don’t want to get too hung up on these details, but just want to establish some parameters for us to imagine an immortal existence.
So in this world now people have a responsibility to themselves that extends far beyond what we could imagine. They know that they can’t maintain any unsustainable habits for any period of time because they’re the ones who will eventually have to deal with the consequences. They know that if they hurt/betray someone else, that person will have all of eternity to hunt them down and exact vengeance. Would this knowledge essentially force people to be kind and respectful to each other, and to act in ways that are far more responsible and empathetic than mortal humans? Or would one person one day decide to break the peace and it would simply end up in eternal conflict?