No Flashes Before Your Eyes did that. This just followed from the main idea and gave us more info about it. Although it was quite a bit Flashes Before Your Eyes was the main introduction.

Desmond has a Constant. Daniel has a Constant.

Game over.

Honestly guys...This Constant thing is going to your heads. I remember after Confirmed Dead people went ghost busting savvy. Now "Constants" are the next cool thing.