"WE pay God honor and reverence, not for His sake (because He is of Himself full of glory to which no creature can add anything), but for our own sake, because by the very fact that we revere and honor God, our mind is subjected to Him; wherein its perfection consists, since a thing is perfected by being subjected to its superior, for instance the body is perfected by being quickened by the soul, and the air by being enlightened by the sun. Now the human mind, in order to be united to God, needs to be guided by the sensible world, since "invisible things . . . are clearly seen, being understood by the things that are made," as the Apostle says (Rom 1:20). Wherefore in the Divine worship it is necessary to make use of corporeal things, that man's mind may be aroused thereby, as by signs, to the spiritual acts by means of which he is united to God. Therefore the internal acts of religion take precedence of the others and belong to religion essentially, while its external acts are secondary, and subordinate to the internal acts."
~St. Thomas Aquinas: Summa Theologiae, II-II, q. 81, a. 7.
