What is the name/term for, "Changing the past gives different outcomes in the future"?

Question

I'm trying to think of the name/ phrase that defines this type of sentence:

"if ___ didn't happen, ___ would have happened and therefore wouldn't/ would ___"

(Or along that basic principal- with nothing specific filling in the gaps)

I'm asking because It's been bugging me all day..

Answer 1

Isn't the theory called "Butterfly Effect"?  There's also a movie that takes that principle and twists it a little, it's called 'The Butterfly Effect', with Ashton Kutcher.