In the pilot episode of Westworld, the Man in Black called Dolores his “old friend,” and asks her, “I’ve been coming here for thirty years, and you still don’t remember me… after everything we’ve been through?” Once William was introduced in the second episode, that conversation became the original foundation for the most popular theory on Westworld: That William is the younger version of The Man in Black, and what we are watching unfold on the series is occurring on two timelines.
The theory has not been completely proven after seven episodes, but the evidence is persuasive. Here are the most convincing clues, so far, suggesting the dual timeline theory where William and the Man in Black are the same person:
Clues that Place William’s Timeline in the Past
— The Westworld logo from William’s timeline…
…is different from the current Westworld logo with the Man in Black.
— Moreover, In episode one (the Man in Black’s timeline) we learn that all diseases have been eradicated. (Ford to Bernard: We can cure any disease, keep even the weakest of us alive and one fine day perhaps we shall even resurrect the dead.”) However, in episode two (William’s timeline), he is asked by the welcoming host if he has an pre-existing health conditions. That suggests that William’s timeline took place long before diseases were eradicated.