How to begin a poem forms an established part of rhetorical theory. But in practice poets know that the solemn celebration of a beginning is something that far transcends rhetoric: the exordium is an inauguration, almost a liturgy which mediates the text's passage and thereby permits it to escape from silence and to enter into the literary universe. At the border between fully poetic speech and speech still outside of poetry, the proem – the preliminary announcement of a poem which follows – is already song and is not yet song. When the poet invokes the Muse to inspire him (or in hymns invokes the divinity to whom the hymn is addressed), he imposes a precise delimitation upon the “contents” of his poem. By indicating its essential themes (this or that story – or part of a story) he outlines the limits of a discourse which was undefined as long as it was merely virtual. In his discussion of the proem, Aristotle defines it in this way: δεῦγμά ἐστιν τοῦ λόγου, ἵνα προειδῶσι περὶ οὗ ὁ λόγος, καὶ μὴ κρήμηται ἡ διάνοια (“the proem provides a sample of the subject, in order that the hearers may know beforehand what it is about, and that the mind may not be kept in suspense,” Rhet. III 1415, a12f.).