We could use trial and error, I guess? Every time we go back, learn a little more, get a little closer to when they decided that they needed something that extreme? Not to mention the why they decided they needed it.

[He still can't wrap his head around it, around Exsilium's past. Even trying to sort out time travel in his head gives him a headache, and the more he thinks about it, the more misgivings about it he's beginning to have.]