Why is imagination closely linked with Romanticism?

As opposed to Enlightenment philosophers who privileged logic and learning, the Romantics felt that emotion and imagination were more vital, important and reliable than logic.  The reason they believed this is that emotion and imagination do not need to be learned; we know how to feel and to imagine without being taught, and so, to them, it seemed more integral to the human experience.  Intense emotion, especially, was thought to be desirable because it is so visceral, and imagination could inspire writers to produce works that would compel this kind of very intense feeling -- like horror -- in the reader.  It is in this way that Mary Shelley's Frankenstein qualifies as a work of Romantic fiction.  The horror produced in the reader from her imaginative descriptions of the creature and his monstrous doings is just the kind of intense emotion prized by Romantics.