I don't know if we can change it. [So many lives would be saved if they could...]

If I tell you now, and you go back and fix things so that the Commonwealth realizes the scope of the Magog threat, then this time line doesn't happen for me. Which means I can't be here now with that knowledge to give you. So if I did tell you, for me to be here telling you means that it didn't work.

...

I hate time travel.