Note: Spoilers for the ending of BioShock: Infinite. If you haven't finished it already, get on that! It's amazing.

One of the biggest debates among BioShock: Infinite fans is the final ending to the game proper. We see Booker DeWitt awake in the all-too familiar office, perhaps with the memories of the alternate lives he's lived fading from his mind like a dream, feeling the need to check on baby Anna. He bursts into the room, runs towards the crib...

...and the game fades to black before we can see whether she is there or not.

There are many who will insist that she isn't there. This simply cannot be true for one obvious reason. Let's get a little philosophical before getting more scientific: The point of the baby-in-the-crib conundrum is the problem itself. Like Schrodinger's cat, until we see inside the crib, baby Anna is both there and not there. As we've seen many times before in this game, we are watching the possibilities collapse into each other, until only one possibility is true. However, this problem actually implies its own solution. There were, theoretically, infinite possibilities, until Elizabeth collapsed them all in order to kill Zachary Comstock in all dimensions at once. We saw her eliminate all other possibilities. There are no more Comstocks. There are no more Elizabeths. Only Bookers and Annas. And if there are no more Comstocks to kidnap the Annas, and no more Elizabeths left for the Annas to become, then why would Anna not be in the crib?

Others say that she is not there because, if you hack the game and move the camera to look inside the crib, there's no baby. But whether the model for baby Anna was actually present in the crib doesn't matter, because, when making a game, developers only model what you can see in the game, i.e., if you can't enter a building, they won't model an interior for it. Why model Anna if you know we're never going to see her?

Another argument against this point is that, perhaps this was the Anna we saw taken by the Comstock from Burial at Sea. I would say that this Comstock is erased from existence technically at the same time as the others. I believe the escape of the final Comstock led to an anomaly, where Elizabeth and Comstock existed, but retroactively ceased to exist once they both died. This universe, as we know, is the same one we see in BioShock. For the sake of clarity, I will call this universe "The Anomaly Timeline." The Anomaly Elizabeth affected this universe, but, at the same time, her fate was sealed. She was already predetermined to disappear with the other Elizabeths at the end of Infinite, after they kill Comstock, same as that Comstock is destined to disappear as well. We the gamers see, in Burial at Sea, years passing and Comstock getting away with it for a while, until Elizabeth shows up and tricks him into getting killed by the Big Daddy. However, what technically "really" happened is, Elizabeth drowned Comstock, and they both ceased to exist in all timelines. It just takes a while for the Anomaly Timeline to "catch up," in a sense.

Notice also how, after Comstock is killed, and all the Elizabeths start to disappear, we see one linger, before the camera cuts away. This is a similar direction technique to when Booker is approaching the crib. Again, the camera cuts away before we get to see what happens. This implies that after disappearing, Elizabeth (and everything else in the tangent universe) snaps back to that moment, when Booker wakes up. After Elizabeth's actions, everything is reset to that moment.

It only makes sense that, for the ending of the game, we would get to see the final possibility. All other possibilities have been destroyed, and collapsed into one timeline. There is now only one Booker, and one Anna.