The truth...behind the truth...behind the truth???

[FullmetalFlamingo]

Ok, so I think its pretty much understood that Ed takes Marcoh's message ("The truth behind the truth") to mean that humans are used to make the philosophers stone, and now that the whole of Amestris is being used for one huge version of that. But what I want to know is if Marcoh was actually talking about that, or if he meant something bigger that involves the truth within the gates? If you have a thought on that I would love to hear it!