In a passage previously quoted Celsus asks us why we do not worship demons, and to his remarks on demons we gave such an answer as seemed to us in accordance with the divine word. After having put this question for the purpose of leading us to the worship of demons, he represents us as answering that it is impossible to serve many masters. “This,” he goes on to say, “is the language of sedition, and is only used by those who separate themselves and stand aloof from all human society.
Those who speak in this way ascribe,” as he supposes, “their own feelings and passions to God. It does hold true among men, that he who is in the service of one master cannot well serve another, because the service which he renders to the one interferes with that which he owes to the other; and no one, therefore, who has already engaged himself to the service of one, must accept that of another. And, in like manner, it is impossible to serve at the same time heroes or demons of different natures.
But in regard to God, who is subject to no suffering or loss, it is,” he thinks, “absurd to be on our guard against serving more gods, as though we had to do with demi-gods, or other spirits of that sort.” He says also, “He who serves many gods does that which is pleasing to the Most High, because he honours that which belongs to Him.” And he adds, “It is indeed wrong to give honour to any to whom God has not given honour.” “Wherefore,” he says, “in honouring and worshipping all belonging to God, we will not displease Him to whom they all belong.”
Source: Against Celsus (New Advent)