It is called the Time Traveler's Paradox. In which a scientist creates a Time Machine and kills their younger self. So now a man who should not- can not- exist, somehow does. That is the Paradox, and Paradoxes are impossible.
1933
2013
1927
2025
2010
1939
2014
2017
1931
2018
2004
1964
2021
1995
2009