He was just showing Israel that He was the true God and not a false God James and they were His witnesses that it was indeed Him. He wanted them to know and believe that it was Him James is all that passage is saying.
Isaiah, chapter 43
"9": Let all the nations be gathered together, and let the people be assembled: who among them can declare this, and shew us former things? let them bring forth their witnesses, that they may be justified: or let them hear, and say, It is truth.
"10": Ye are my witnesses, saith the LORD, and my servant whom I have chosen: that ye may know and believe me, and understand that I am he: before me there was no God formed, neither shall there be after me.
"11": I, even I, am the LORD; and beside me there is no saviour.
"12": I have declared, and have saved, and I have shewed, when there was no strange god among you: therefore ye are my witnesses, saith the LORD, that I am God.
"13": Yea, before the day was I am he; and there is none that can deliver out of my hand: I will work, and who shall let it?
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