Nice anthill you're digging up!
I think we can agree that logic is definable, not open to interpretation, but logic is hardly useful in understanding our personal nature, is it?
I think a great example is how fiction can take on a life of its own. If the author focuses on simple, specific story, the truths drawn from it can be applicable to a vast amount of people. However, if fiction is strict, outlining its own meaning at the end of the story, the truths are limited to the context of the story. Instead of the experience being interpreted, the overall message is interpreted instead, usually with a "yes or no" whether the reader accepts it.
In fiction, at least, I think it's simply a matter of honesty. A person can THINK they believe something, but it is only true to the self (in my opinion) if you feel it. When Gandalf says that what is important is "what we do with the time that is given us", is his statement true? How do we know what the RIGHT thing to do with the time given us is? All we know is whether or not we agree with the statement. If we agree, then we accept that there IS a right and wrong.
We can think things like this in our heads, but do we KNOW whether or not it is true? A personal conclusion, I think.