The Talmud (Megillah 7a) tries to prove that Megillas Esther was composed with Divine Inspiration:
It has been taught: R. Eleazar said: Esther was composed under the inspiration of the holy spirit, as it says, And Haman said in his heart.
This is referring to the part of the story where Haman paid the king a late night visit:
So Haman came in. And the king said to him, What shall be done to the man whom the king delights to honor? Now Haman thought in his heart, To whom would the king delight to do honor more than to myself?
The proof seems to that the authors could not have known what Haman thought in his heart without Divine Inspiration. But even ignoring Haman's internal thoughts, how would the authors have known the conversation that took place in the kings private chambers? Is there any evidence that someone told them the contents of the conversation? If not, shouldn't this itself be the proof of Divine Inspiration?