Bioshock infinite question (spoilers)

[Maximum Clutch]

I don't know if I missed a major piece of the story or something, but if Booker and Comstock are the same person, how are the two of them able to be in the same room together, and how is Booker able to kill him?

[Guest Frogger24]

They are the same person but alternate versions of that same person. When Booker went to get baptised after the battle of Wounded Knee his choice split into two different futures for himself. In one version he refuses and remains "Booker" while in the other he accepts redemption and becomes Comstock.

 

They exist together due to the confluence of alternate universes or realities which were breached by Rosalind Lutece. Due to that meddling Comstock stole Bookers child. Thus came Elizabeth. Eventually the "Lutece twins" (really they are just alternate versions of one person) bring "Booker" into a reality where the events of Bioshock Infinite take place.

 

In essence they are the same person taken from two different realities/universes and tossed into the same universe/reality.

 

Does that help?

[Minuette]

I believe Frogger does sum it all up in one go. 

I like to think of the movie Looper to help you out. So after Bookers gambling debt and after he gave them the baby, he became depressed and wanted to be a new man so he got baptised and became Zachary Comstock who wanted his baby back so he created a time machine sort of thing to go and grab the girl which loops back to the beginning where Booker gave the baby away.

There's many different theories on how the ending might work out, this one is one of many.

[Elite]

He's the same person because of Mass Effect fields.

I've never played Bioshock Infinite, that's just the answer.

[D-38 Boss]

Bioshock Infinite is based around the Multiverse theory, where there are multiple timelines, all with different situations, so in separate timelines, DeWitt and Comstock are the same person.