Having made this important discovery after his return from Geneva, Shelley determined to communicate it to the world in a poem, which should teach its readers that incest was nothing but an imaginary sin; that ceasing to have the show of sin, on being rightly regarded, it was seen to be compatible with the highest virtue; that it was one of the great ‘multitude of artificial vices,’ to whose existence the fewness of ‘real virtues’ was referable; that instead of being loathsome, nauseous, hideous, unutterably repulsive and sinful, the conjugal union of a brother and sister under the Free Contract was permissible in the eyes of philosophic moralists, and compatible with moral purity and the finest delicacy in the brother and sister; that besides being altogether permissible, and in no degree reprehensible, this conjugal union was a virtuous relation, in which brothers and sisters would often stand towards one another in a rightly-constituted society. To put this social doctrine before the world, in the form most likely to commend it to the feelings of youthful readers, and induce them to further every movement for a state of things, in which brothers and sisters could so live together without offending their neighbours, Shelley wrote _Laon and Cythna: or, The Revolution of the Golden City: a Vision of the Nineteenth Century. In the Stanza of Spenser._ Brother and sister of the same parents, Laon and Cythna, the hero and heroine of the poem, are beings endowed with all the virtues conceivable in perfect human nature, and are still enjoying the scenes of their childhood in Argolis, when they pass from the state of mutual affection, that is desirable in a brother of some sixteen or eighteen summers and a sister (_ætat._ 12), to a state of mutual love that is desirable only between young people who can in the ordinary course of things marry one another. What follows from this state of things is indicated with consummate delicacy by the poet, too wary and artful to shock his readers in the second canto by clear disclosures, that might determine them to refrain from perusing any later canto of a long poem. Laon and Cythna are suddenly torn asunder by the agents of the tyrant, who figures in the poem as a type of European monarchs in the nineteenth century, and soon after their severance Cythna gives birth to the lovely child who owes her life to Laon. In a later passage of the narrative, after he has been released from the cage on the column’s top, and she, after divers painful experiences, has been proclaimed the prophetess and supreme directress of the revolutionists of the Golden City, Laon and Cythna come together under circumstances, which prevent them from recognizing one another in the first hour of their reunion. Laon is still uncertain whether she is really his sister, or only bears a strong resemblance to her, when he hears Cythna harangue the Golden City revolutionists in these words:--