Why is Saint Denis said to be the proponent of Gothic architecture?

The Abbey of Saint Denis was rebuilt from 1135 - 1144 under the watchful eye of its abbot, Suger, a schoolfellow of the King. Although Saint Denis' position in the evolution of Gothic architecture is disputed, many attribute it as the first of the genus. It is argued that at Saint Denis we can encounter the first examples of Gothic arches, (pointed load-bearing stone structures) and walls of dazzlingly coloured stained-glass, producing the theory of 'luxa nova' or the 'New Light of God’, where before there was only heavy stone. Suger oversaw the stone-carving on the exterior of the magnificent building, designing some of the first tympanums on the portals of the transept doors and long, elegant jamb statues. No expense was spared on the reconstruction of Saint Denis, with fierce opponents condemning the ostentation of Suger's spending, citing his extravagance as inappropriate and unnecessary for the worship of God. Nevertheless, this is a building which catalysed the 'Gothic' style throughout Europe, engendering the trend of churches and cathedrals competing with one another, endeavouring to be bigger and better than their neighbour, in order to ascertain the attention of their God.