Around the middle of the twelfth century, the nature of the Christian church was transformed with the invention -- by the Abbe Suger at St-Denis -- of a new style, later to be derided by Renaissance classicists as 'Gothic'. Whereas Romanesque architecture was dark and massive, Gothic was light both in terms of mass and in its goal of flooding spaces with light. The style evolved to match a theology of light -- light as a manifestation of God's grace, essential for life, growth, and healing.Gothic architects developed virtuoso arrangements of columns and pointed arches -- in effect skeletons in which walls had no structural role, and which stood up because the forces set up by one arch in a series are counteracted by those of its neighbours. As the style matured, this idea was lost sight of, and the formerly load-transmitting elements became decoration, webs of ribs masking rather than elucidating structure.