Messing with Time

Paycheck reminded me a lot of A Sound of Thunder by Ray Bradbury. They both brought up similar issues about messing with time. Should we be allowed to interfere with time for profit? In Paycheck, Jennings messes with the future to secure his own future and of course to profit with the company. It never quite goes into the time consequences of his actions, but his taking over Rethrick could have severely altered time. Rethrick could have brought on this oppressive society just by building and operating a time scope. So much can be changed with such insignificant things, like the one butterfly in A Sound of Thunder. Just building the time scope itself altered must have altered the future drastically.