Good sermon. It mainly draws to mind the point in the Easter Vigil liturgy when the deacon chants "Christ our light!"
"For, by its immensity, the divine substance surpasses every form that our intellect reaches. Thus we are unable to apprehend it by knowing what it is. Yet we are able to have some knowledge of it by knowing what it is not." - St. Thomas Aquinas, Summa contra gentiles, I, 14.