The Romantic poets were very moved by nature, dreams and visions, and individuality. For the Romantics, imagination was personified through the imagery of nature. These poets sometimes relied upon their dreams, creations of the imagination (like Coleridge, Milton, and Keats).
For the Romantics, the imagination was the ultimate creative power. It "was elevated to a position as the supreme faculty of the mind." Through this, humans were able to parallel the creativity of the divine (or of G/god). (This idea is known as pantheism: the view in which nature and G/god are identical.)
Imagination is also important, for the Romantics, based upon the fact that it (the imagination) was used to interpret nature (nature being something the Romantics relied heavily upon in regards to symbolism and imagery).