What happens when the "truth" isn't factual? One of the eternal questions for religious people in their ongoing attempts to rationalise their inherently irrational systems of belief.
On the other hand, any system based on a rational view of the world (i.e. fact based), is much more easily able to change its view of what is true when new evidence comes in. This's why things like Science actually works and why secular (vs. theocratic) societies tend to be much more successful and nicer places to live.