Board Thread:Questions and Answers/@comment-28265951-20160421125919/@comment-28555794-20160526022931

The one important thing that we cannot forget here is the theory of time paradox.

Putting aside how Eobard Thawne's time travelling affected The Flash's timeline in Season 1, Eddie's sacrifice was itself a paradox. Eddie sacrificed himself, which erases Eobard from existence. But then if Eobard was erased from existence, there would be no need for Eddie to sacrifice himself.

So yes, that is why the singularity happened. And by having the Flash & Firestorm prevent its completion, The Flash's timeline (from the beginning of Season 1) remains intact.

In order for the Flash's timeline to remain intact, the past MUST happen. And the past includes The Reverse Flash travelling back in time, from the future, to kill Nora Allen (with the intent of killing young Barry) in the year 2000.

Now, this is where the writers, as is usual in time-travel plots, start making rules that are convenient for their plots...

Speedsters are supposed to be "protected" from time travel paradoxes. This is why in "The Reverse Flash Returns", Cisco begins to be erased from existence, but not Barry or Eobard Thawne. And by "protected", what they probably mean is that the Speedforce brings them into existence where/when the timeline requires.

So in other words, once Barry's timeline reaches the point where Eobard travelled back in time to learn what time period he's from, The Speed Force brings Eobard into existence, then takes him away. And then when his timeline reaches the point where Eobard travelled back to the year 2000 and killed Barry's mother, The Speed Force will bring him into existence again, for that purpose.

But, Barry's timeline most likely will continue to be a timeline where Eobard was never born. But Barry will most likely be dead by that time.