The main theme of Bioshock Infinite is the existence of parallel universes and an ability to move between them. So, there is no secret anymore that Booker DeWitt and Comstock – the protagonist and antagonist of the game – are the same person that made different choices in these parallel universes.
But this gamer theory states that Booker is also Andrew Ryan, another antagonist in Bioshock Infinite. This can be proven by following Elizabeth and Booker to the underwater city of Rapture in the DLC titled “Burial at Sea”. There is a bathysphere that can be controlled only by Andrew Ryan through the process of checking his DNA. And guess what, Booker DeWitt passed the test.
This means that he is not only Comstock, but also Andrew Ryan. Bioshock Infinite is one weird game, isn’t it?