An angel, then, is an intelligent essence, in perpetual motion, with free-will, incorporeal, ministering to God, having obtained by grace an immortal nature: and the Creator alone knows the form and limitation of its essence. But all that we can understand is, that it is incorporeal and immaterial. For all that is compared with God Who alone is incomparable, we find to be dense and material. For in reality only the Deity is immaterial and incorporeal.