"I do not know which of us has written this page.

I have no way of knowing whether the events that I am about to narrate are effects or causes.
I have no way of knowing whether the events that I am about to narrate are effects or causes.

I have no way of knowing whether the events that I am about to narrate are effects or causes.
I have no way of knowing whether the events that I am about to narrate are effects or causes.