Friedrich Wilhelm Joseph von Schelling (1775–1854), looking back at Kant's work a generation later, judged that Kant, by failing to demonstrate the validity of human perception, had left a dichotomy between the human mind and external reality. His own Naturphilosophie was meant to heal that rupture, and imagination played a central role in his endeavor. It was crucial for Schelling that imagination was both human and divine. God possesses imagination in its fullness, and the divine imagination (die göttliche Einbildungskraft) is "the generating power of the universe" (Engell, p. 304). The human imagination shares in this faculty, though on a lower level: ordinary mortals in the power to perceive unity in the multiplicity of our experience; the creative genius in the ability to create new unity out of existing things. Imagination is not apart from nature, it is present as a power in nature from the beginning of creation. Here the distinction between natura naturata and natura naturans, inherited from the medieval Scholastics, is important. Natura naturata is the created sensible object, whether it be a natural being or the product of a human creative act—a poem or painting or piece of music. The natura naturans is the active power of imagination itself, a quickening spirit giving life and energy to all being, including the human mind; it is, in effect, God present as an active force in the world. Thus imagination, as the natura naturans, is the living link not only between the human mind and the external world but between the created world and the transcendent.
The Romantic poet and thinker Samuel Taylor Coleridge (1772–1834), although he wrote no single treatise on the imagination, is arguably the central figure in its modern development. He drew heavily on most of the major work that preceded him, including the biblical, classical, and medieval sources, as well as the most important thinkers of the century before him such as Leibniz, Tetens, and Kant and contemporaries like Schelling. Coleridge offered no system to support his view of imagination, but the insights and arguments scattered throughout his works finally yield a coherent and important perspective. His most influential work of literary theory and criticism is his Biographia Literaria (1817), in which he both acknowledges his debts to such thinkers as Kant and Schelling and at times diverges significantly from them. His locus classicus on imagination (chapter 13) distinguishes between primary and secondary imagination, and between imagination and fancy. Primary imagination is "the living Power and prime Agent of all human Perception, and as a repetition in the finite mind of the eternal act of creation in the infinite I AM." The secondary is "an echo of the former, co-existing with the conscious will"; it "dissolves, diffuses, dissipates, in order to re-create." The lesser faculty of fancy is only a "mode of Memory," dealing with "fixities and definites," with sensible realities rather than with "ideas." This view of imagination is clearly similar to Schelling's: primary imagination is the faculty by which all human beings shape their experience of the world into meaningful perception; secondary imagination is the artist's ability to create new shapes and meaning out of existing material. It is also similar in its strong affirmation of the relationship between the human and divine imaginations: the human creative act participates in the infinite creative act of God, from which it derives its power.
Coleridge's view of imagination is intimately related to his conception of idea and symbol. An idea is a suprasensible reality incarnated in sense images; it is the product of all the human faculties—reason, understanding, sense—working under the unifying power of the imagination. An idea "cannot be conveyed but by a symbol" (chapter 9), which is a product of the imagination. As Coleridge writes in the Statesman's Manual (1816), symbols are "the living educts of the Imagination; of that reconciling and mediatory power, which incorporating the Reason in Images of the Sense … gives birth to a system of symbols, harmonious in themselves, and consubstantial with the truths, of which they are the conductors." Coleridge's conception differs significantly from Kant's, in that the ideas thus incarnated, including such ideas as God and immortality, are not merely regulative (as in Kant) but are truly constitutive of reality.
Other important Romantic explorations of imagination include the prophetic poetry of William Blake (1757–1827) and the Defence of Poetry of Percy Bysshe Shelley (1792–1822), both of which affirm the transcendent reach of imagination, and so are generally congruent with Coleridge and William Hazlitt's (1778–1830) essays and the letters of John Keats (1795–1821), which offer a more secular view but still affirm the unifying power of imagination.