KirkFan, Marsden is trying to point out you've constructed a classic "grandfather paradox". You travel backwards in time to "correct" or "improve" a condition, but in doing so, you negate the very reason for traveling back in time.
Sincerely,
Bill
I was mostly just joking, I swear I heard Billy Crystal when I typed that about the proofs but I can't remember from what. I thought it might have been something Miracle Max said, but I'm not sure. Maybe it was Zoidberg.
Actually that applies to anything whatsoever you do back in time. So in essence, what you're saying is that time travel is impossible. Let me explain: No matter what you do in the past, it will become part of your history, making it useless to go back to do the thing in the first place, but if you don't go back then the need to travel back in time will exist. No matter what you do (travel back or not) you'll end up with a paradox. The only solution is that time travel is impossible.
Unless you have a microwave oven and jiffy pop, but you run the risk of becoming your own grandpa.