John Calvin on Idols and God's Incomprehensible Essence

"It is true that the Lord occasionally manifested this presence by certain signs, so that he was said be been face to face; but all the signs he ever employed were in apt accordance with the scheme of doctrine, and, at the same time, gave plain intimation of this incomprehensible essence.  For the cloud, and smoke, and flame, though they were symbols of heavenly glory (Deut 4:11), curbed men's minds as with a bridle, that they might not attempt to penetrate farther.  Therefore, even Moses (to whom, of all men, God manifested himself most familiarly) was not permitted though he prayed for it, to behold that face, but received for answer, the the [brightness] was too great for man (Exod 33:20).

"The Holy Spirit appeared under the form of a dove, but as it instantly vanished, who does not see that in this symbol of a moment, the faithful were admonished to regard the Spirit as invisible, to be contented with his power and grace, and not call for any external figure?  God sometimes appeared in the form of a man, but this was in anticipation of the future revelation in Christ, and therefore did not give the Jews the least pretest for setting up a symbol of Deity under the human form.

"The mercy-seat, also (Exod 25:17, 18, 21), where, under the Law, God exhibited the presence of his power, was so framed, as to intimate that God is best seen when the mind rises in admiration above itself: the cherubim with outstretched wings shaded, and the veil covered it, while the remoteness of the place was in itself a sufficient concealment.  It is therefore mere infatuation to attempt to defend images of God and the saints by the example of the cherubim.  For what, pray, did these figures mean, if not that images are unfit to represent the mysteries of God, since they were so formed as to cover the mercy-seat with their wings, thereby concealing the view of God, not only from the eye, but from every human sense, and curbing presumption?  To this we may add, that the prophets depict the seraphim, who are exhibited to us in vision, as having their faces veiled; thus intimating, that the [brightness] of the divine glory is so great, that even the angels cannot gaze upon it directly, while the minute beams which sparkle in the face of angels are shrouded from our view.  Moreover, all men of sound judgment acknowledge that the cherubim in question belonged to the old tutelage of the law.  It is absurd, therefore, to bring them forward as an example of our age.  For that period of [childish silliness], if I may so express it, to which such rudiments were adapted, has passed away.

"And surely it is disgraceful, that heathen writers should be more skillful interpreters of Scripture than the papists.  Juvenal (Satire, 14) holds up the Jews to derision for worshiping the thin clouds and firmament.  This he does perversely and [disrespectfully]; still, in denying that any visible shape of Deity existed among them, he speaks more accurately than the papists, who [foolishly talk] about there having been some visible image.  In the fact that the people every now and then rushed forth with boiling haste in pursuit of idols, just like water gushing forth with violence from a copious spring, let us learn how prone our nature is to idolatry, that we may not, by throwing the whole blame of a common vice upon the Jews, be led away by vain and sinful enticements to sleep the sleep of death" (Institutes of the Christian Religion, John Calvin).