- Grandfather Paradox - Seems you could go back in time and cause your ancestors not to meet. HOWEVER = Contradiction as this would mean your birth didn't occur but you exist. Marty prevents his birth, but must exist to have done so, which entails his birth cannot have been prevented. Does this make time travel impossible?
- Paradox - either both true and false at the same time, or neither.
- Responses to Grandfather Paradox - Coincidenes eg. Killing Hitler and the gun jams. OR A police force who intervene when paradoxes occur OR Reapers who 'mend…