Very good question, and I am not totally qualified to answer this thoroughly, but I will try. Jesus said he IS the Truth, and I believe we can understand it in this way.
He said he created all things, to accept that means that the world/universe that exists and that we live in, was designed by him. He established how things work and they,.i.e. sun moon, our atmosphere, the oceans, gravity, fire, etc. all of them were created by design and for purpose.
Proverbs 3:19-20 says "The LORD by wisdom hath founded the earth; by understanding hath he established the heavens.
NOW LET ME PLEASE INTERJECT to help understand my point!!
We humans were also created for a reason, with purpose, designed by God. But at the same time we have the ability/power to choose to obey or not. The results of our disobedience to God's design are hatred, murder, greed, theft, guilt, shame , regret and many more egregious things . And why because they are contrary to the way we are designed. But free will gets in the way of God 's design and the results are all the terrible things in this world.
Now Take a train for example, it is designed for a purpose to move materials, liquids , people etc, from one location to another. And although it is very powerful and can be very productive for society, that would drastically change if it jumped off the track designed for it move on. It then becomes useless to the point it can't function as it was originally designed. Not atleast until it GETS BACK ON TRACK
Why do I say all this, because he is emphasizing that there is No thought, belief, object, that is right, that is profitable, whether material or spiritual that he did not create. So then for anyone to say there are other beliefs, truths, objects that were somehow made by something or someone else, they are wrong. It is not truth, but a Lie, and regrettably all of us have chosen to do and believe things our way opposed to God's.
Jesus as creator Dictates Truth. Determines Truth. Anything is either counterfeit or in direct opposite to the Truth if it is against or opposite to what JESUS HAS SPOKEN. After all there is nothing that exists that was not created by him, so he alone establishes what is right and what is wrong. What is and what isn't. It is impossible for him to speak anything BUT TRUTH. Because by definition everything he speaks is his design and has it's origin in the one who created all living things.