User blog comment:The Milkman/Reaper Logic/@comment-2127388-20120425203841/@comment-4950455-20120426013612

''Me, personally, would like to know if the Indoctrination theory is correct, and than how Harbinger would know about Catalyst, or on the opposite, how would Protheans, or generations before, know that Catalyst even exists, when Sheaprd is the first one to actually meet him. Another small thing which isnt revealed. ''

From what I understand, the indoctrination theory assumes that the Catalyst (at least as we meet it at the ending) is a fiction created by the indoctrination process and/or a representation of Harbinger itself. But yeah, that's confusing in any theory.