Isaiah 37:18

18.and 19.Truly, O Jehovah. Here Hezekiah begins to distinguish between the false gods and the true God, which we also ought to do very carefully. Wicked men, who have no light, indulge in some confused imaginations about God, which quickly pass away, so that they think that there is no God, or care nothing about him. (53) But God does not wish that his people shall be moved by a slight and passing opinion, but that he shall be acknowledged by them as the true God, who drives away all superstitions by the brightness of his power. (54) It is not; enough, therefore, that we believe in something which heathens imagine to be a deity, but we must believe in God in such a manner as to distinguish him from pretended gods, and to separate truth from falsehood; and, indeed, when he has once shone into our hearts, those false religions which formerly occupied our minds immediately give way.

This doctrine ought to be the more carefully held, because many persons rest satisfied with dark speculations, and think that it is enough if they acknowledge some deity. They evidently do not know whether they ought to worship the God of the Mahometans or of the Jews; and fly in the air, so that, as the saying is, they neither touch heaven nor earth. Nothing can be more destructive than this imagination; for it mingles and confounds idols with God, whose majesty does not hold its due rank. if it does not reign in solitary grandeur over the ruins of all the false gods. Thus the beginning of true piety is, that from the whole multitude of false gods we shall wisely distinguish that one God to whom we ought to be entirely devoted.