society placed on architecture was the design of churches. In the seventh book of De re aedificatoria, Alberti laid out his idea of the perfect church--based on the notion of incorporating classical elements into a building that needed to express Christian beliefs. For Alberti, churches had to stir up people's piety by "entertaining them with the admiration of their beauty" (quoted in Greenhalgh 129). The beauty that was to be found in architecture was based on the perfection inherent in the use of 'perfect' geometrical forms, i.e., the circle and the square. In Alberti's view, beauty was "the result of a mathematical formula based on reason, in which nothing can be added or taken away without spoiling the whole" (Greenhalgh 129). Thus, for the highest calling of architecture, Alberti saw the centrally-planned church as the most beautiful, hence the most appropriate, form.
This idea did not originate with Alberti however. Brunelleschi had already begun to use variations of this idea in his buildings. Examples include the organization of the Old Sacristy of St. Lorenzo (designed in 1419), and the Pazzi Chapel (1430 or later). Yet, Brunelleschi never achieved a church that was entirely on a central plan until after, Greenhalgh speculates, he met the young Alberti (Greenhalgh 125). Brunelleschi's S. Maria degli Angeli (1434-1437) was the first building in which Brunelleschi entirely rejected the Gothic form of wide side aisles, that provided support for the spans of the roof. He also rejected the cross-shape in favor of the self-contained circle that reflected such ancient works as the Pantheon at Rome. Even if S. Maria degli Angeli was produced under Alberti's influence, however, Brunelleschi, from his own limited knowledge of antiquity, had been moving toward the idea of a centrally planned church. Brunelleschi had always based his work on geometry, believing in the power of "sphere and cube, and exact proportional relat...