An analysis of the role that philosophies and philosophical structures which were circulating in seventeenth-century Rome played in the designs of the Baroque architect Francesco Borromini, especially in the church of San Carlo alle Quattro Fontane. The analysis includes a historical reconstruction of the setting of seventeenth-century Rome and an examination of drawings and built work in relation to published diagrams and essays, which were translated by Borromini into geometries and architectural forms.

Chapters: 1. Renaissance Precedent: Leon Battista Alberti; 2. The Structure of the Cosmos in the Baroque; 3. The Neoplatonic Idea at the Accademia di San Luca; 4. Syncretism and Architectural Syntax; 5. The Structuring of the Conceptual Process; 6. Athanasius Kircher and Hermeticism; 7. Esoteric Symbols of Hermetic and Neoplatonic Philosophy; 8. Light, Vision and Numerology; 9. The Transmutation of Geometries; 10. Neoplatonic Philosophy; 11. Presocratic Origins