This scene from The Shawshank Redemption, which my wife and I just watched for the first time, reflects the same idea I was trying to articulate today.
Dufresne said to his friends, after he got out of the hole, that the music that he had with him—the Mozart that he had with him in his head—was his and could not be taken away by anyone. He said it goes beyond stones and walls; yes, but it begins with them. It cannot begin to exist without them, and when it takes hold in the heart, it begins to live without them.
The same is poetry, the art of which the medium is thought.
Thanks, dear reader, should you ever find me, for being my gadfly.