I can of myself do nothing. As I hear, I judge, and my judgment is righteous; because I don't seek my own will, but the will of my Father who sent me.
If I bear witness of myself, my witness is not true ...  This means, "But you are rejecting my witness of myself because I am the one witnessing." It is as if Jesus had said, "Oh yes, I read what you are thinking, namely, that if I bear witness of myself, my witness is not true."  Thus this verse is a line of the conversation which the Pharisees did not utter, but which Jesus read out of their hearts.  Without for a moment yielding any of the authority of his own witness, the Lord immediately marshaled other witnesses.  It is as if he said, "Well, all right, since you reject my witness because I gave it, we shall call other witnesses.  The first to be called was God himself.  See under  John 8:13.