Cool discussion
What is the dividing line between statements we can call objectively true or false, and statements which are subjective?
I posit, as a start, that we might be able to draw a dividing line at statements which say something about intention.
Now, I haven't thought about this too intensely yet, but, at first glance, it seems like statements that say nothing about intentions can be provably true or false, based on the accepted definitions of terms used in the statement.
"The sky is blue" (define: sky, blue)
"Abraham Lincoln was the 16th President of the U.S." (who am I referring to, what does 16th mean, what is the President of the U.S.)
On the other hand, "Abraham Lincoln wanted to free the slaves" is an unprovable statement--you can find evidence to support arguments, but--and here's the kicker--even if all the evidence points to Ol' Abe wanting to free the slaves, we can't get inside his head to know.
What other guidelines can be drawn?
As MicroBalrog pointed out, how do we classify statements as axiomatic?
I read somewhere that a good way to define an axiomatic statement is "a statement which cannot be opposed without implicitly relying on it."
e.g. you need to be alive (and allowed to live) to assert that one has no right to life.
On the other hand, "A man has the right to the fruit of his labor" is not axiomatic, as I need not possess any material goods to posit that no one has a right to them.