From "A Defense of Poetry" by Shelley

... Poetry is the record of the best and happiest moments of the happiest and best minds. We are aware of evanescent visitations of thought and feeling sometimes associated with place or person, sometimes regarding our own mind alone, and always arising unforeseen and departing unbidden, but elevating and delightful beyond all expression: so that even in the desire and the regret they leave, there cannot but be pleasure, participating as it does in the nature of its object. It is as it were the interpenetration of a diviner nature through our own; but its footsteps are like those of a wind over a sea, which the coming calm erases, and whose traces remain only as on the wrinkled sand which paves it. These and corresponding conditions of being are experienced principally by those of the most delicate sensibility and the most enlarged imagination; and the state of mind produced by them is at war with every base desire. The enthusiasm of virtue, love, patriotism, and friendship is essentially linked with these emotions, and whilst they last, self appears as what it is, an atom to a Universe. Poets are not only subject to these experiences as subjects of the most refined organization, but they can colour all that they combine with the evanescent hues of this ethereal world; a word, or a trait in the representation of a scene or a passion, will touch the enchanted chord, and reanimate, in those who have ever experienced these emotions, the sleeping, the cold, the buried images of the past. Poetry thus makes immortal all that is best and most beautiful in the world; it arrests the vanishing apparitions which haunt the interlunations of life, and veiling them or in language or in form sends them forth among mankind, bearing sweet news of kindred joy to those with whom their sisters abide - abide, because there is no portal of expression from the caverns of the spirit which they inhabit into the universe of things. Poetry redeems from decay the visitations of the divinity in man...