The bootstrap paradox.

 

      The bootstrap paradox is a hypothetical situation that arises when time travel is involved and which seems to contradict the laws of cause and effect. It involves a person traveling back in time and giving an object or information to their past self, which would mean that the object or information has no clear origin. For example, suppose a person travels back in time and gives their past self a book that they wrote in the future. 

   This would mean that the book has no clear author because the person's future self wrote the book based on the information they received from their past self. This creates a paradox because it suggests that the book exists without having been created, which seems to violate the laws of cause and effect. It is important to note that the bootstrap paradox is purely theoretical and is not necessarily indicative of the nature of time travel.