Nor can it be said, as some have maintained, that "these visible sacrifices are fitting with regard to other gods, and that to the most high God, as being better than those others, better sacrifices, namely, the service of a pure mind, should be offered" [*Augustine, as quoted below]. The reason is that, as Augustine says (De Civ. Dei x, 19), "external sacrifices are signs of internal, just as audible words are signs of things. Wherefore, just as by prayer and praise we utter significant words to Him, and offer to Him in our hearts the things they signify, so too in our sacrifices we ought to realize that we should offer a visible sacrifice to no other than to Him Whose invisible sacrifice we ourselves should be in our hearts."
Others held that the outward worship of latria should be given to idols, not as though it were something good or fitting in itself, but as being in harmony with the general custom. Thus Augustine (De Civ. Dei vi, 10) quotes Seneca as saying: "We shall adore," says he, "in such a way as to remember that our worship is in accordance with custom rather than with the reality": and (De Vera Relig. v) Augustine says that "we must not seek religion from the philosophers, who accepted the same things for sacred, as did the people; and gave utterance in the schools to various and contrary opinions about the nature of their gods, and the sovereign good." This error was embraced also by certain heretics [*The Helcesaitae], who affirmed that it is not wrong for one who is seized in time of persecution to worship idols outwardly so long as he keeps the faith in his heart.
But this is evidently false. For since outward worship is a sign of the inward worship, just as it is a wicked lie to affirm the contrary of what one holds inwardly of the true faith so too is it a wicked falsehood to pay outward worship to anything counter to the sentiments of one's heart. Wherefore Augustine condemns Seneca (De Civ. Dei vi, 10) in that "his worship of idols was so much the more infamous forasmuch as the things he did dishonestly were so done by him that the people believed him to act honestly."
Reply Obj. 1: Neither in the Tabernacle or Temple of the Old Law, nor again now in the Church are images set up that the worship of latria may be paid to them, but for the purpose of signification, in order that belief in the excellence of angels and saints may be impressed and confirmed in the mind of man. It is different with the image of Christ, to which latria is due on account of His Divinity, as we shall state in the Third Part (Q. 25, A. 3).
The Replies to the Second and Third Objections are evident from what has been said above. _______________________
THIRD ARTICLE [II-II, Q. 94, Art. 3]
Whether Idolatry Is the Gravest of Sins?
Objection 1: It would seem that idolatry is not the gravest of sins. The worst is opposed to the best (Ethic. viii, 10). But interior worship, which consists of faith, hope and charity, is better than external worship. Therefore unbelief, despair and hatred of God, which are opposed to internal worship, are graver sins than idolatry, which is opposed to external worship.
Obj. 2: Further, the more a sin is against God the more grievous it is. Now, seemingly, a man acts more directly against God by blaspheming, or denying the faith, than by giving God's worship to another, which pertains to idolatry. Therefore blasphemy and denial of the faith are more grievous sins than idolatry.
Obj. 3: Further, it seems that lesser evils are punished with greater evils. But the sin of idolatry was punished with the sin against nature, as stated in Rom. 1:26. Therefore the sin against nature is a graver sin than idolatry.