In the second oration Gregory lays down the position referred to above, that it is impossible for even the most exalted human reason fully to grasp the Nature of God, though His Existence is patent to all.  We can only, he says, predicate negatives concerning Him.  He gives three reasons for this incapacity.  First to enhance our estimation of this knowledge, when attained hereafter; secondly to save us from the danger of falling through pride, like Lucifer, if we attained it prematurely; and thirdly, to support and sustain us in the trials and conflicts of this life, by the certainty that its attainment hereafter will be the reward of faithful service in them.  The cause of our present inability is the body with which our soul is united, the grossness of whose present condition hinders us from rising to the complete apprehension of the invisible and immaterial.  God, out of compassion for our weakness, has been pleased to designate Himself in Holy Scripture by various names taken from material objects, or from moral virtues; but these are only stepping-stones to the truth, and have indeed been sometimes perverted, and made a basis for polytheism.  It is, however, only natural that the Divine Essence should be shrouded in Mystery, for the same is the case with the created essences also.