The relations between W. B. Yeats's A Visionand Oswald Spengler's The Decline of the West(vol. 1, 1918 and 1922; vol. 2, 1923)1 have received comparatively more critical attention than other intertextual connections of Yeats's historical system. This is due, in part, to Yeats's famous declaration that the close resemblance between Spengler's historical morphology and his own conception of history was so uncanny, so profound, that if the German's works had been translated and published in English before A Vision A(1925), he could not have completed his elucidation of the system (L716). Thomas Whitaker explains when Yeats encountered Spengler's theory of the rise and fall of civilizations he was so startled that he “excitedly suspected occult influences.”2 This sentiment is expressed in A Vision Bwhere Yeats writes:

It is not surprising given Yeats's own emphasis on the similarities between A Vision'shistorical conception and Spengler's morphological interpretation of history that various scholars have sought to highlight those features that are common to both accounts of human development.

Scholars have, for the most part, emphasized two conceptual features that are shared by A Visionand The Decline of the West. First, their studies have stressed that both accounts of history employ similar “years of crisis,” and that the excited Yeats saw this resemblance as stemming from a shared supernatural source and influence. These studies accord with Yeats's explanation that the corresponding “years of crisis,” employed in both accounts of European history, are proof that his historical schema posited tenable theoretical principles. Kevin McNeilly argues that Yeats viewed the similarities between A Vision's method of representation and Spengler's periodical historicism as being ”objective evidence for the correctness of his assumptions about the cosmic order and for the validity of the mystical, divinely–inspired sources of [A Vision]: his so–called ‘instructors.’ ”