1. John of Salisbury, Metalogicon, ed. C.C.J. Webb (Oxford, 1929), Book 3, ch.4, p.136.
2. R.W. Southern, The Making of the Middle Ages (London, 1953), pp.63–7; Petrarch’s letter is in Ernst Cassirer et al. (eds.), The Renaissance Philosophy of Man (Chicago, 1948), p.142.
3. Purgatorio, canti 4–26; R.W.B. Lewis, Dante (London, 2001), pp.132–44.
4. Thomas Aquinas, Summa Theologica, Latin text and English translations, 61 vols. (London and New York, 1964–81), II(i), quaestio 84, articles 1–4, vol. 26, pp.61–79.
5. For an illustration, see Millard Meiss, Painting in Florence and Siena after the Black Death (Princeton, NJ, 1951), P1.71.