Last night, Faraday set out to disprove his theory of "what happened, happened," by trying to change the past. However, it seems like trying to disprove his theory already happened, thus validating his original theory.
Confused? I'll elaborate, but watch the clip, and let Faraday explain in his own words what he's attempting to do, now that he has realized that humans—with their free will—are the "variables" that he never accounted for in his scientific research.
The major shocker (that wasn't very shocking to me because I totally called it!) is that Widmore is Faraday's father.