Objection 1: It would seem that there should not have been many ceremonial precepts. For those things which conduce to an end should be proportionate to that end. But the ceremonial precepts, as stated above (AA. 1, 2), are ordained to the worship of God, and to the foreshadowing of Christ. Now "there is but one God, of Whom are all things . . . and one Lord Jesus Christ, by Whom are all things" (1 Cor. 8:6). Therefore there should not have been many ceremonial precepts.
Obj. 2: Further, the great number of the ceremonial precepts was an occasion of transgression, according to the words of Peter (Acts 15:10): "Why tempt you God, to put a yoke upon the necks of the disciples, which neither our fathers nor we have been able to bear?" Now the transgression of the Divine precepts is an obstacle to man's salvation. Since, therefore, every law should conduce to man's salvation, as Isidore says (Etym. v, 3), it seems that the ceremonial precepts should not have been given in great number.
Obj. 3: Further, the ceremonial precepts referred to the outward and bodily worship of God, as stated above (A. 2). But the Law should have lessened this bodily worship: since it directed men to Christ, Who taught them to worship God "in spirit and in truth," as stated in John 4:23. Therefore there should not have been many ceremonial precepts.
On the contrary, (Osee 8:12): "I shall write to them [Vulg.: 'him'] My manifold laws"; and (Job 11:6): "That He might show thee the secrets of His wisdom, and that His Law is manifold."
I answer that, As stated above (Q. 96, A. 1), every law is given to a people. Now a people contains two kinds of men: some, prone to evil, who have to be coerced by the precepts of the law, as stated above (Q. 95, A. 1); some, inclined to good, either from nature or from custom, or rather from grace; and the like have to be taught and improved by means of the precepts of the law. Accordingly, with regard to both kinds of men it was expedient that the Old Law should contain many ceremonial precepts. For in that people there were many prone to idolatry; wherefore it was necessary to recall them by means of ceremonial precepts from the worship of idols to the worship of God. And since men served idols in many ways, it was necessary on the other hand to devise many means of repressing every single one: and again, to lay many obligations on such like men, in order that being burdened, as it were, by their duties to the Divine worship, they might have no time for the service of idols. As to those who were inclined to good, it was again necessary that there should be many ceremonial precepts; both because thus their mind turned to God in many ways, and more continually; and because the mystery of Christ, which was foreshadowed by these ceremonial precepts, brought many boons to the world, and afforded men many considerations, which needed to be signified by various ceremonies.
Reply Obj. 1: When that which conduces to an end is sufficient to conduce thereto, then one such thing suffices for one end: thus one remedy, if it be efficacious, suffices sometimes to restore men to health, and then the remedy needs not to be repeated. But when that which conduces to an end is weak and imperfect, it needs to be multiplied: thus many remedies are given to a sick man, when one is not enough to heal him. Now the ceremonies of the Old Law were weak and imperfect, both for representing the mystery of Christ, on account of its surpassing excellence; and for subjugating men's minds to God. Hence the Apostle says (Heb. 7:18, 19): "There is a setting aside of the former commandment because of the weakness and unprofitableness thereof, for the law brought nothing to perfection." Consequently these ceremonies needed to be in great number.
Reply Obj. 2: A wise lawgiver should suffer lesser transgressions, that the greater may be avoided. And therefore, in order to avoid the sin of idolatry, and the pride which would arise in the hearts of the Jews, were they to fulfil all the precepts of the Law, the fact that they would in consequence find many occasions of disobedience did not prevent God from giving them many ceremonial precepts.
Reply Obj. 3: The Old Law lessened bodily worship in many ways. Thus it forbade sacrifices to be offered in every place and by any person. Many such like things did it enact for the lessening of bodily worship; as Rabbi Moses, the Egyptian testifies (Doct. Perplex. iii). Nevertheless it behooved not to attenuate the bodily worship of God so much as to allow men to fall away into the worship of idols.