Furthermore, it is self-evident that truth exists, for whoever denies the existence of truth simultaneously concedes its existence. If truth does not exist, then it is true that truth does not exist; yet if something is true, then truth exists. God, however, is truth itself. "I am the way, the truth and the life" (Jn. 14:6). Therefore God's existence is self-evident.
This quashes relativism in a paragraph. If one says, as relativists do, “there is no truth,” one is immediately contradicting oneself—for the claim that there is no truth must itself be untrue.
Therefore, with certainty, truth exists. If we define God as truth, it follows that God necessarily exists.