The windows of the Gothic cathedral and the emphasis on light as it flooded these enormous and majestic buildings are perhaps its most salient characteristic. It makes sense, then, that the architect would have appreciated the theological significance of light. Saint Augustine had conceived of human beings' acquisition of knowledge in terms of divine illumination: God enlightens the mind with knowledge. This idea of God pouring light into the minds of men proved a potent metaphor for architects in the Gothic tradition, in which physical light was meant to evoke thoughts of its divine source.
Quoted from How The Catholic Church Built Western Civilization by Thomas Woods, Jr., Ph.D.
