In the late 15th Century, the doctrine of the Virgin's immaculacy was strongly promoted by the Franciscan order, especially under Pope Sixtus IV, himself a Franciscan. As a consequence, two offices of the Immaculate Conception were written by Bernardino de' Busti and Leonardo de Nogarolis, and proved highly influential on the iconography of paintings on the theme. In view of the fact that there was no established way of representing what was in effect a new subject, artists and patrons approached the problem in a variety of ways. However, one type of representation, of which the present picture is an early example, eventually came to predominate. In it the Virgin is shown in glory, surrounded by a number of attributes drawn from a variety of biblical texts, which were associated with her immaculacy. Many of these texts are also quoted in the offices of the Immaculate Conception.
At the top of the panel is the diminutive figure of God the Father with the words 'Tota Pvlcra es, amica mea, et macvla non est in te' ('Thou art all fair, my love; there is no spot in thee', Song of Solomon, IV, 7). There follows a sequence of epithets, most of which are drawn from the Song of Solomon: 'Electa vt sol' ('Clear as the sun', VI,10), 'Pvlcra vt lvna' ('Fair as the moon', VI,10), 'Tvrris David' ('Tower of David', IV,4), 'Fons Ortorvm' ('Fountain of Gardens', IV,15), 'Sicvt Lilivm' ('As the Lily [among thorns]', II,2), 'Pvtevs Aqvarvm ('A well of living waters', IV,15), 'Ortvs Conclvsvs' ('A garden enclosed', IV, 12). Three are from the Book of Ecclesiasticus: 'Cedrvs exaltata in Libano' ('A cedar raised up in Lebanon', XXIV,17), 'Oliva Speciosa' ('Splendid Olive', XXIV,19), 'Plantacio Rose' ('Plantation of Roses', XXIV,18), while the rest have no direct source in the Bible: 'Stella Mare Star of the Sea'), 'Porta Celi' ('Gate of Heaven'), and 'Civitas Dei' ('City of God'). Further associated texts are inscribed on the framing elements in the spandrels. Even in a period which had a limited respect for the virtues of brevity, there can have been few more comprehensive treatments of this particular subject.