My wife and I saw Looper the other day. Unlike Doc Rampage, we were able to suspend our disbelief long enough to enjoy the movie. It was fun, although a little bit too bloody for my wife's liking. She also found the main sex scene completely gratuitous. Since we saw the movie, though, she's been pointing out a steady stream of plot holes to me, and I've been doing my best to patch them up, though not necessarily successfully.
Everything beyond this point is full of spoilers, so beware.
The premise is that in the future, time travel has been invented. However, it's completely illegal, so only criminals use it, and they use it to dispose of bodies. A victim is kidnapped and sent back in time by about thirty years, where a looper immediately shoots him, disposes of the body, and is paid. Since the victim's still alive and well at the time when his future self is shot and killed, no one misses him, his body can be incinerated with no one the wiser at the earlier time, and no incriminating body around in the future. If the premise sounds a little silly, it is, and it mainly exists for the fact that eventually the looper must "close the loop." Eventually, the person sent back in time is himself, thirty years in the future, and he's required to shoot and kill him (victims always have their faces covered, so the looper doesn't know that he's killed himself until after the fact). Then he receives a tremendous payday, retires, and has thirty years until the criminal gang picks him up and sends him back in time to be killed by himself.
So what happens when the looper his future self go go? It's a death sentence for his future self. For his present self, it's something worse. And here is where the whole time travel premise has some logical problems. In one scene, when the future looper escapes, they catch the present looper. Then they start cutting off pieces. Those pieces start vanishing off the future looper until he comes back to be properly executed. They can't just kill the present looper, since that would create a dangerous paradox. But damaging him is allowed.
Doc had a lot of trouble with this one, as did my wife. Does it really make sense for pieces to start disappearing in real time? It does for the audience, but would the looper notice it in real time, as for him, it happened thirty years ago. And this is where you either accept the premise of how time travel works in the movie or you don't. The future looper has only a fuzzy memory of the time between the time he's been sent back to and the time when he was sent back. That's because what happens between those two points isn't set: it's possibilities. Those memories only become clear when they happen in the present. Thus, the future looper can realize that his current self is being mutilated, because those memories are becoming clear, and realizing what's going on, he has motivation to go back. Because his entire life is being rewritten, and the past thirty years are becoming worse and worse as his body becomes less and less whole.
So the difference is, I could accept this premise. At least as a premise of a movie--I'd have a hard time accepting it in a Physics lecture. Doc, and to a lesser extent, my wife, couldn't.
In this story, the future looper is sent back and escapes, and he sets out to kill the person who sent him back. And in the present time, that person is a small child. The present looper is determined to kill the future looper, because he thinks it's the only way he can get his life back.
The main problem I had, and the contradiction I had the biggest trouble with, was that the future looper remembered killing himself the first time around. How was he able to change that the second time around? How could anything be different?
The second problem I had is that it was presented that the small boy who was sending all the loopers back in the future was seeking revenge because of what the future looper did when he was sent back. But if, in the first timeline, he was sent back and killed without incident, then how could the boy have needed to have revenge for anything, in order to send him back in the first place?
The bottom line, of course, is that time travel always causes paradoxes. Read Doc's post for even more time travel logic puzzles aka plot holes.