Hugh Blair (1718-1800), Lectures on Rhetoric and Belles Lettres
(London: Charles Daly, 1839), p. 526 (from Lecture XXXIX):
It was not till men had begun to be assembled in great cities, after the distinctions of rank and station were formed, and the bustle of courts and large societies was known, that pastoral poetry assumed its present form. Men then began to look back upon the more simple and innocent life, which their forefathers led, or which, at least, they fancied them to have led: they looked back upon it with pleasure; and in those rural scenes, and pastoral occupations, imagining a degree of felicity to take place, superior to what they now enjoyed, conceived the idea of celebrating it in poetry. It was in the court of King Ptolemy that Theocritus wrote the first pastorals with which we are acquainted; and, in the court of Augustus, he was imitated by Virgil.
But whatever may have been the origin of pastoral poetry, it is, undoubtedly, a natural, and very agreeable form of poetical composition. It recalls to our imagination, those gay scenes, and pleasing views of nature, which commonly are the delight of our childhood and youth; and to which, in more advanced years, the greatest part of men recur with pleasure. It exhibits to us a life, with which we are accustomed to associate the ideas of peace, of leisure, and of innocence; and, therefore, we readily set open our heart to such representations as promise to banish from our thoughts the cares of the world, and to transport us into calm Elysian regions.