This brings us to the true function of decoration in a twelfth-century book. It was clearly not just because it was pretty. The twelfth century was an age which delighted in classification and ordering of knowledge. Its most admired writers, men like Peter Lombard and Gratian, arranged and shuffled information into order that was accessible and easy to use. Twelfth-century readers loved encyclopedias…Les us then consider book illumination in these terms. It suddenly becomes easy to understand. Initials mark the beginning of books or chapters (PL.85). They make a manuscript easy to use. It helps classify the priorities of the text…A newspaper does this today with headlines of different sizes…any reader of a modern newspaper will fiercely defend his choice of paper by praising the text, not the layout or illustrations. It is not surprising that the twelfth-century chroniclers from St. Albans, Lincoln, and Canterbury complimented the accuracy of manuscripts when what they meant was that they liked using them.

Christopher De Hamel, A History of Illuminated Manuscripts 99.