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.