Francesco Borromini and the Cultural Context of Kepler’s Harmonice Mundi

The idea of circular domed architecture as imitative of the flat earth covered by the 'Dome of Heaven' was established from Byzantine times up to its revival during the Renaissance. Yet the cosmological symbolism of the circular dome was replaced in the early seventeenth century when elliptical, oval or other geometrically-inspired domes became a key feature of the Baroque. The move away from circular to oval or elliptical forms by architects such as Borromini coincides with the new cosmology and Kepler's view of elliptical orbits as the basis for the structure of the universe. Building on his Mysterium Cosmographicum (1596) and the view of perfect, regular nested solids as the basis for the organisation of the planets, Kepler focused on the ellipse as underlying the mechanics of the universe. His realisation that the universe was not based on perfect circular motion but on elliptical orbits (with the sun at one of the foci) was developed in Harmonice Mundi, linked to concepts of harmony and proportion. In turn, the work of the architect Borromini (as at S. Carlo alle Quattro Fontane 1638-41 and S. Ivo della Sapienza 1642) involve novel and complex geometric designs that significantly align Kepler's astronomical ideas. Mathematical precision underlies Borromini's seemingly extravagant schemes, in the same way that Kepler's theories sought harmony in the universe. Documentary evidence to substantiate a claim of the influence of Kepler’s theories on Borromini has yet to be found. However, it is significant that Borromini's patron in Rome was Cardinal Barberini (later Pope Urban VIII) who was well-known for his interest in astronomy. Kepler's mathematical methodology and interpretation of the geometrical structure of the universe may have appealed to Borromini and his patrons on many levels. It cannot be mere coincidence that the use of such mathematical forms in ecclesiastical architecture comes in at around the same times as Kepler's writings.