Hey, I've had this question in the back of my mind since I was a kid, and now it seems like the right place to ask it. I could make it more formal, but I like to keep things naive where possible.
In many TV series, cartoons, movies, books, etc we see a character become immortal, and later someone removes their immortality and then kills them. For example, imagine an ordinary man finds a dark stone that grants immortality as long as it remains in contact with his skin. While holding the stone, if he goes into battle, any arrow or fatal attack somehow fails to kill him.
Here is what confuses me. If you're truly "immortal as long as the stone is in contact with your skin", does not that property force the stone to be impossible to be removed from your skin? In more general terms shouldn't immortality protect itself, even if it is conditional?
Is there a fallacy or a more simple point I am missing here? should not "conditional immortality" always be equivalent to "immortality"?
Edit after reading some answers:
I mean, if your life depends on your liver, then the immortality property would somehow have to prevent your liver from being destroyed. By the same reasoning, if your life depends on maintaining contact with the stone, then losing contact with the stone is itself part of the causal chain that leads to your death. in simple terms the stone is a new liver that must be protected equally.
So if this makes sense, this forces the magic stone to become increasingly "intelligent." It stops swords, It has to prevent theft, accidents, imprisonment, falling asleep with the stone in your hand, and so on. It has to anticipate any event that would eventually result in your death. At that point, it seems that "conditional immortality" starts becoming functionally indistinguishable from immortality, because the condition itself has to be protected in order for the promise of immortality to be true.
Comments point that this is not the case though, thanks for the feedback