Have you ever had a false belief? Have you ever had an expectation or prediction and been let down or surprised? When you’re trying to make up your mind about what is true, do you look inward or outward?
If truth is relative, there’s nothing to “figure out.” If it were it would not be truth. It would be a belief or observation. Not all observations are true but they may not be false; the same goes for belief. Truth is not subjective. Truth must be absolute true or false. Otherwise you have no foundation, no standard by which to judge something else. We seek standards so that we may not be decieved but do not always see what is true. It requires an open mind to examine ones beliefs and determine if they are true or false and replace them if false. It also requires examining standards that conflict until a harmony is found.
Truth is used, to know the relative differences between observations and beliefs. I use a standard truth of what a meter is to indicate I am 1.8 m tall and you are say 2 m tall. I can truthfully believe you are taller than me relatively speaking. But the truth of that stands alone, unchangeable.
A truth that is relative can be changed when the relation changes. Then you find that what you believed was true was in fact not. Therefore it was not actually be truth but belief.
Truth is also not what we want it to be, but what it is. The one that changes according to follow truth is free and also powerful. Knowledge of things that are true is power.
Evidence from the world is irrelevant to your beliefs. They are already true simply by virtue of your having them, and there’s no reason to change them in the light of new evidence.