Insanity of Insanity

The insanity of insanity is that sanity is insanity. With out insanity you can never be sane because then you'd always be insane, and without sanity; mankind wouldn't have been able to define insanity. Because it takes a sane person to know what an insane person is. Even if the insane one is actually the sane one. Its just the sane one believes that he's sane and the insane one believes he's sane as well. So to what point is it that humanity is actually sane or insane? Because to say that you're sane could mean that you're actually insane or vise versa. And to claim to be sane would even BE insane considering no one knows where the difference is. I wonder where the line is that holds the two (sanity/insanity) in separation?