For the development of nationhood from one or more ethnicities, by far the most important and widely present factor is that of an extensively used vernacular literature. A long struggle against an external threat may also have a significant effect as, in some circumstances, does state formation, though the latter may well have no national effect whatever elsewhere. A nation may precede or follow a state of its own but it is certainly assisted by it to a greater self-consciousness. Most such developments are stimulated by the ideal of a nation-state and of the world as a society of nations originally 'imagined', if you like the word, through the mirror of the Bible, Europe's primary textbook, but turned into a formal political philosophy no earlier than the nineteenth century and then next to canonised by President Woodrow Wilson and the Versailles peace settlement of 1920.