There is a ghost of one of Tiber Septim's soldiers in Old Hroldan Inn. I didn't think much of this until I spoke to him and referred to me as Hjalti. This is big in my opinion, as it verifies "The Arcturian Heresy". Even better, when I finished the quest, he taught me fighting moves which were originally imparted by "Sword masters of Alcaire". Hooray! Finally evidence that Arcturian Heresy is true, and that Tiber Septim was from High Rock!

You mean: Finally evidence that Arcturian Heresy has truth, and that Hjalti was from High Rock!

I doubt the writer of that book would have intended part of the book to be true and the rest to be false. It's written in too straightforward a manner, and a primary source proving one part true pretty much proves the whole thing in my opinion.

It would be a hell of a feat to come up with an entire lie the size of that account without including ANY truth in it. Impossible, in fact.
Just because an account contains some facts does not AT ALL mean that everything it says is fact.

"George Washington was man from Virginia who became the first President of the United States of Canada."
See?

I completely agree that the Arcturian Heresy is truth, or at least a sort of truth. There's never been much doubt of that in my mind. But your reasoning is silly, no offense.