Coming out of the Romanesque style of architecture, which is massive, dark and heavy with no consideration for light, is Gothic architecture which is light, open and airy. Gothic cathedrals were erected with soaring heights, flying buttresses and pointed arches allowing for the building of large clerestory windows. Through this revolutionary design a great amount of light floods into the buildings. Gothic cathedrals were regarded as images of the City of God, and light added an impressive spiritual element to the buildings.
To those who were familiar with Romanesque churches, visiting a Gothic church must have been a religious experience in and of itself. These cathedrals changed the whole vibe of who God is. The design of the buildings directs the eye upwards, where light is brought in from the heavens and gives one the feeling of a heavenly presence on Earth. This light reinforced the idea as God as the welcoming light of the world. God was portrayed as compassionate and loving, rather than a harsh and judgmental object of fear, as in Romanesque churches.
Several years ago I was fortunate enough to visit the Notre Dame cathedral in Paris. I recall walking through the door and being confronted from the far end of the structure by a large highly illuminated Pieta.I can't recall by what means the statue was lit up, nor can I find that information, but what I do remember is the sense of awe that struck me. It was as if the statue had been lit just for me, which goes to show that even today the role of light in Gothic cathedrals has a profound effect on the human psyche.