Relative to the set of facts concerning the actual past (the time traveler's younger self survived and is alive today), the time traveler cannot retro-kill their younger self because the past cannot be changed.
(as used in discussions about time travel logic and paradoxes)
The idea that history is fixed and permanent—once something has happened, it's impossible to alter what actually occurred, even if you go back in time.
Time traveler's younger self(as used in the time travel paradox scenario)
The earlier version of a person who traveled through time, referring to when that person was younger before they built the time machine.
retro-kill(Time-travel thought experiments)
The act of a time traveler killing a person in the past, particularly a version of themselves or an ancestor whose survival is a precondition of the time traveler's existence.
A way out of the paradox was suggested by David Lewis (1976) who argued that the ability of killing somebody should be understood as a possibility compossible with the relevant fact. As an opera singer, for example, you are able to sing operas, since you have the physical capacity and training to do so, but because of a temporary loss of voice, you cannot hum a single tune. What you can do relative to one set of facts, is something you cannot do relative to another set of facts. This contextual