Von Simson's "The Gothic Cathedral" is a profound and deeply illuminating exploration of the cultural, religious, and aesthetic factors that shaped the development of those magnificent cathedrals of France beginning in the mid-twelfth century. In the light of his extensive preperatory analysis of medieval aesthetics and theology, he delves into two case studies, Abbott Suger's St.-Denis in the outskirts of present-day Paris, and the Notre Dame Cathedral of Chartres. The former cathedral is the first full-fleged Gothic edifice; the latter is widely viewed as the masterpiece of the style.
Browsing through Thomas Aquinas, I stumbled upon a portion of his analysis of the Trinity in which he states that beauty requires three attributes: 1) integrity or wholeness; 2) harmony or proper proportion; and 3) intelligible radiance. These correspond exactly to the cardinal aesthetic virtues that von Simson identifies as guiding the Gothic imagination. The theory is rooted ultimately in the Neoplatonist philosophers - especially Plotinus and Proclus. It was transmitted to the great minds of the High Middle Ages through the line of Augustine, Boethius, and especially Pseudo-Dionysius the Areopagite, whose influence on Gothic cathedrals can hardly be over-stated.
The basic idea is that the human sense of beauty corresponds to natural consonances, or integer relationships that are intrinsically harmonious. In music, it is observed that the simplest possible integer ratios in string length (1:2, 2:3, and 3:4) correspond to the perfect intervals and the octave. These ratios are believed to correspond to the deep structure of the cosmos.
Following the mystical cosmology of Pseudo-Dionysius, the theologians of the High Middle Ages suppose that through the contemplation of harmonious relationship, the mind can be led to the contemplation of pure ideas, and by the contemplation of pure ideas, the mind can find an analogous path upward to God. This capacity of abstract ideas to direct the mind heavenward is called the anagogical principle.
So we find in the Gothic Cathedral an ordered set of relations in the overall design, corresponding to the core religious and mathematical constructs. While the preceding Romanesque cathedral was a kind of canvas that contained and presented iconic paintings and statues, the Gothic cathedral is itself is the work of art, immediately and directly rending an image of the ideal forms that mediate between the mind and God.
Von Simson lays this all out in a most persuasive and exciting fashion. As a great fan of Pseudo-Dionysius myself, I was staggered to learn of the decisive role he had in guiding the explicit conceptual basis for the construction of these magnificent structures.
There is much more to the book, including a thorough history of the fascinating and singular figure of Abbott Suger. Von Simson traces his seminal influence on everything from politics to aesthetics to the composition of the Chansons des Gestes.
The final third of the book is given to an exhaustive study of Chartres, including an interesting consideration of the role of festivals in Medieval life and the cathedral movement, and a brief exploration of the cult of the Virgin Mary. For, if St.-Denis is the temple of Pseudo-Dionysius, Notre Dame de Chartres is without question a temple of the Great Goddess in Christian guise. She is overwhelmingly the controlling archetype of that magnificent creation.
It's an electrifying book, copiously illustrated with dozens of pictures - though take care to note that plate references are inexplicably given in the margin. I had to go back and re-read an entire chapter after noticing them.
If you're interested in the larger cultural and historical context of the Gothic cathedral, it would be difficult to imagine a better book. My only criticism is that it would have been appropriate for the frequent Latin quotations to be translated into English, as this book was written for a general audience as well as medievalists.