Hence it is not surprising that the [Manichean] heretics, who say that God is not the author of our body, blame these bodily observances being paid to God. In which censure they evidently fail to remember that they themselves are men, not seeing that sensible representations are necessary to us for inward knowledge and affection. For it is experimentally shown that our soul is excited by bodily acts to think and feel: hence we properly use such acts to raise our mind to God.
In the payment of these bodily observances the cult, or worship, of God is said to consist. For we are said to cultivate those objects to which we pay attention by our works. Now we busy ourselves in paying attention to the things of God, not as though we were of service to Him, as is the case when we are said to tend, or cultivate, other things by our attentions, but because such actions are of service to ourselves, enabling us to come nearer to God.* And because by inward acts we go straight to God, therefore it is by inward acts properly that we worship God: nevertheless outward acts also belong to the cult, or worship, of God, inasmuch as by such acts our mind is raised to God, as has been said.
Hence the worship of God is also called religion, because by such acts a man in some sort binds (ligat) himself, that his thought may not wander astray from God; and also because by a sort of natural instinct he feels himself bound (obligatum) to God, that in such manner as he can he should pay reverence to Him from whom is the origin of his being and of all his good.*
Hence also religion has received the name of piety, for piety is that whereby we pay due honour to parents: hence aptly the honour paid to God, parent of all, is taken to be a part of piety, and they who oppose the worship of God are called impious.
But because not only is God cause and origin of our being, but our whole being is in His power, and all that is in us is His due, and thereby He is truly our Lord and Master, therefore what we perform in honour of God is called service. Now God is our master not by accident, as one man is another's master, but by nature; and therefore the service that we owe to God is quite different from that whereby we are accidentally subject to a man, the dominion of man over man being partial, and derivative from God. Hence the service specially due to God is called among the Greeks latria.*
3.118 : That by Divine Law men are obliged to a Right Faith
3.120 : That the Worship of Latria is to be paid to God alone