To know what we state or ...

It certainly seems reasonable to know everything we can know about the statements we utter. Is it, however reasonable to say what is without knowing it all.
It is possible we have not yet attained knowing of a certain fact, but in the process of argument or even a monologue one comes to it. Such knowledge by insight does happen occasionally. Just recently I attempted to convince my friend of his error when I suddenly understood my own mistake. The endeavour concluded with an insight of just such a nature!