Thou hast heard... — The appeal is to the conscience of the exiles. They had heard the prediction. They are bidden to consider it all. Should not they declare the impression it had made on them?
I have shewed thee. — Better, I shew thee, as a present incipient act.
New things. — The “new things” are those that lie in a more distant future than the conquests of Cyrus, which are referred to as “former things.”