Medieval churches and cathedrals were supposed to be images of the heavenly Jerusalem. Hence Romanesque churches are nearly always decorated with pictures of mosaics of Christ reigning in majesty, and nearly always over the porch of the main entrance to cathedrals there was an image of the last judgment. You passed through the last judgment in order to enter the heavenly sanctuary, and indeed one of the most outstanding examples of this was the porch of Fulbert’s cathedral, left standing after the great fire and incorporated into the new cathedral as it still stands today. But this architecture had always thought of churches as portrayals of the heavenly city. The new architecture saw it differently. Under the influence of the Cistercians who were the pioneers of the new style, imaginary pictures and pictorial symbols of the heavenly Jerusalem were done way with. Now the geometric proportions of the church were themselves the symbols of the heavenly city, and not only the symbols, but the very principles upon which God had created the world. To enter the cathedral was not merely to imagine but actually to enter into the depths of the divine, and the aesthetic pleasure gained from the contemplation of the proportions a foretaste of the very joys of heaven.
It is hard for us to grasp that Chartres was not built as we would build a cathedral today, paying careful attention, and indeed cash, to its construction because it is the house of God. Chartres was built by people in the grip of an intense mystical fervour. It is, of course, notoriously easy to be led astray by number mysticism and this has happened, without doubt, to some students of Chartres. As critics have pointed out , if you look for a mathematical relationship you can nearly always find it somewhere. The length of the whole cathedral from porch to apse, for example, has been calculated to be almost 365 units of medieval measurement, and thus related to the days of the year. This has been alighted on with corroborative joy but is almost certainly fortuitous, for it does not reflect the underlying Platonic philosophy. But so many features do we cannot doubt that number mysticism underlay the cathedral’s conception. In Augustine’s aesthetic the most perfect form was that of a square because its sides are in the relation of 1:1, and in other cathedrals built at this time the relation of nave to crossing is that of a perfect square. The master of Chartres, however was not able to do this, as he was constrained by the foundations of the old cathedral, but he solved his problem in a most ingenious way.
The ratio of width to length in the crossing is not that of a square but 16.44 to 13.99, but this, it turns out, is the ratio of one side of a pentagon to the diameter of a circle enclosing the pentagon. It is also that of the so-called golden section. Variations of this golden section relationship are found in more and more intricate instances throughout the cathedral. The length of one side of a decagon inscribed inside the same circle as that enclosing the pentagon is 8.64 metres. This is the height of the piers above the ground. The lower stringcourse of the triforium again divides the vertical shafts rising from the columns below them at the level of the golden section. The length of two bays of the aisles is equal to the width of the nave, which is again equal to the height of the lower stringcourse above the nave.
Of course, there is nothing especially Christian about the golden section, it was used by the Greeks to build the Parthenon. But given what we know about the theology of the school at Chartres it is inconceivable that Augustine’s mystical aesthetic was not the philosophical foundation upon which the cathedral was built. It is these proportions that are responsible, above all, for its extraordinary aesthetic appeal. But it was a philosophy that went beyond that of the Greeks. To experience beauty is to participate in the divine, because beauty is in essence mathematical and mathematics is the first expression of God’s being in the world. This is what is important to me and transformational, I think, of our experiences of beauty. I wouldn’t want to put it in the same terms that the Platonists of the school of Chartres used. I would want to say that there is another dimension beyond this one that we presently inhabit, and that natural beauty is not just a pleasant experience that we happen to have but the evidence of the presence of this further dimension shining through the transparencies of our own.
Chartres inspires me to think that the discoveries scientists are making that are increasingly inseparable from the mathematics that describe them, are not just conveniently described by mathematics. In entering into the secrets of the universe scientists are entering into the divine. There is a deep religious emotion that is the corollary of the intellectual discoveries that science makes. Chartres is the expression of that emotion.