In the first half of the fifteenth century, sculpture in Florence broke new ground in the field of expressive naturalism. Although Donatello's sculpture best demonstrates this, this article suggests that the impulse for it came from Brunelleschi whose few new surviving sculptures were seminal for its development. The achievement of both sculptors is identified as a new awareness of the relationship between the sculpted figure and the viewer. This can be seen in the way the placement of figures was used to enhance both naturalism and meaning. Naturalism was achieved partly by adapting their forms to give the illusion of actual presence particularly when viewed from below, and partly by taking into account their relationship to their environment. Meaning was achieved by reassessing the physical and spiritual import of each individual figure. The combination of these innovations encouraged the viewer to seek a new immediacy and depth in his religious experience. 

Donatello's Ascension of St. John the Evangelist belongs within the larger sepulchral iconography of the Old Sacristy of San Lorenzo. In Donatello's relief, there is a donor-like figure that has not been discussed by scholars. This article argues that this figure most probably represents Giovanni di Bicci de' Medici, the original patron of the sacristy, and that Donatello's Ascension formed part of a posthumous commemoration of Giovanni ordered by his sons. In establishing this identification, evidence is presented that suggests that Brunelleschi's supposed disapproval of Donatello's work in the sacristy arose less from problems of stylistic incompatibility than from the position of the sacristy as a monument caught between two generations of Medici with differing conceptions of Giovanni's commemoration.