TTTP1 Everything is set

This theory assumes that all time is set and all actions are also set. Therefore if one was to travel back in time the events in which would be caused by his actions had already happened. This theory does not answer the lack of tourists from the future, but would mean that any actions a time traveller wishes to do would have already happened. An example would be: A man thinks his girlfriend is cheating on him after coming home from work and seeing his bed sheets slept in and a man leaving his house in the distance. A man wishes travel back in time to check before asking his girlfriend to see if she was cheating on him. He goes back to the time to before the events would have happened. He bumps into his girlfriend and one thing leads to another and they get together in the bed. He then realises he has got to leave quickly because he is about to come in from work. The man then realises his girlfriend never cheated on him and that it was him that slept in the bed.

This would mean any event a time traveller did would not matter because it had already happened. The problem with this is the time traveller may feel secure with knowing this and attempt to change history. Another example: A man hates his dad because his dad cheated on his mother and then killed them both leaving him to be brought up in care. He hates him so much he wants to kill him. The man time travels back to a time before his dad ever met his mum. He planed to shoot him, so he brought his gun and aimed it and fired it. His dad was shoot in the chest but survived and events where unchanged. This was because he was unaware that his dad was shot back before his dad met his mother and the nurse was his mother. This did not change events.

But what would happen if he had shot his dad in the head or tried to go back? Philosopher David Lewis has a theory that time would prevent any events happening that would change time. There for a bird would fly in the way or he would not be able to find his dad etc. This would also mean that it would be unable to prevent him from not being born.

Given this theory it is also possible that although humans are meant to be set going forwards (till backwards time travel), other entities may travel back. Humans use memory to know where we have been and witness what is currently happening. The biggest problem with something going the other way would be changing history. If everything is set it is likeier there are objects that could exist by remembering what is going to happen and see what has happened.