Nietzsche once wrote that "Convictions are more dangerous foes of truth than lies." And of course the begged question is what is truth then? How does one define it and validate it. Can that even happen? Do we kill truth be the simple process of definition?
From convictions truth becomes irrelevant. Convictions force truth to be what it wants it to be. In religion, conviction would make a deity truth. The quest then would be to cast off convictions to know truth. But how does one do that? How does one even have any idea what convictions are?
If we believe in something, then it is a conviction. Worse still, "all things are subject to interpretation whichever interpretation prevails at a given time is a function of power and not truth." In the Dark Ages, the Church determined what was truth through its immense power. It silenced Copernicus and Galileo. It burned those who questioned their autonomy. So the question of truth gets murkier as we try to de-wed ourselves of the influence of religion.
Left stark and bare, we can only assume that Nietzsche is saying truth is. Or I suppose more correctly, truth was. It is a thing that can't be defined but has one true definition. Its like the Mohist saying that no matter where you look at a stream, you are seeing the beginning, middle, and end all at once. It is the beginning the flows from where you look, the middle of the entire stream, and the end of where it came from. It is truth.
Truth can never flow from definition or conviction. Truth is what exists and it must be something that can never have a definition. Truth just is.