When John of the Cross was a schoolboy in the Jesuit College of Medina del Campo, he was introduced to the art of rhetoric by a gifted teacher, Juan Bonifacio. ¹ The standard textbook at the time was a classical manual of the first century, the Rhetorica ad Herrenium, which detailed the techniques involved in composing, memorising and declaiming a text and the figures of speech that constitute an effective style. ² Its teachings left their mark on John’s later writings, including his long poem, the Cántico espiritual, which employs many of the figures that the Rhetorica describes. ³ One of them is chiasmus, the placing in parallel of two contrasted concepts and statements, the second of which reverses the order of the elements in the first. ⁴ The Rhetorica terms it commutatio (reciprocal change), and commends it warmly: ‘one cannot deny that the effect is neat when in juxtaposing contrasted ideas the words are also transposed’. ⁵ The pages that follow examine the incidence of chiasmus in the poem (Cántico A), and its implications for our understanding of how it was composed. ⁶