Given the Incarnation, crucifixion, and Resurrection happened, it follows the Church is required.
1 Since, however (as has already been said), the death of Christ is, so to say, the universal cause of human salvation, and since a universal cause must he applied singly to each of its effects, it was necessary to show men some remedies through which the benefit of Christ’s death could somehow be conjoined to them. It is of this sort, of course, that the sacraments of the Church are said to be.
2 Now, remedies of this kind had to be handed on with some visible signs.
3 First, indeed, because just as He does for all other things, so also for man, God provides according to his condition. Now, man’s condition is such that he is brought to grasp the spiritual and intelligible naturally through the senses. Therefore, spiritual remedies had to be given to men under sensible signs.
4 Second, because instruments must be proportioned to their first cause. But the first and universal cause of human salvation is the incarnate Word, as is clear from the foregoing. Therefore, harmoniously the remedies by which the power of the universal cause reaches men had a likeness to that cause—, that is, the divine power operates in them under visible signs.
5 Third, because man fell into sin by clinging unduly to visible things. Therefore, that one might not believe visible things evil of their nature, and that for this reason those clinging to them had sinned, it was fitting that through the visible things themselves the remedies of salvation be applied to men. Consequently, it would appear that visible things are good of their nature—as created by God, but they become damaging to men so far as one clings to them in a disordered way, and saving so far as one uses them in an ordered way.
6 Thus, of course, one excludes the error of certain heretics who want every visible thing of this kind removed from the sacraments of the Church. Nor need one marvel at this, for the very same men maintain that whatever is visible is evil in its nature, and is produced by an evil author. And this we rejected in Book II.
7 Nor is it unsuitable that by things visible and bodily a spiritual salvation is served. For visible things of this kind are the instruments, so to say, of a God who was made flesh and suffered. Now, an instrument does not operate by the power of its nature, but by the power of its principal agent who puts it into operation. Thus, also, then, do visible things of this kind work out a spiritual salvation; not by a property of their own nature, but by Christ’s institution, and from the latter they receive their instrumental power.
1 However, since the spiritual remedies of salvation (as was said) have been given to men under sensible signs, it was suitable also to distinguish the remedies provided for the spiritual life after the likeness of bodily life.
2 Now, in bodily life we find a twofold order: for some propagate and order the bodily life in others; and some are propagated and ordered in the bodily life.
3 Now, in a bodily and natural life three things are necessary of themselves, and a fourth incidentally. For first, by generation or birth a thing must receive life; second, by growth it must arrive at its due size and strength; third, both for the preservation of life acquired by generation and for growth nourishment is necessary. And these are of themselves necessities for natural life, because without these bodily life cannot be perfected; wherefore, one assigns to the vegetative soul which is the principle of life the three natural powers: that of generation, that of growth, and that of nourishment. But, since there can be an impediment to natural life from which the living thing grows weak, a fourth thing is incidentally necessary; this is the healing of the sick living thing.
4 Thus, then, in the spiritual life, also, the first thing is spiritual generation: by baptism; the second is spiritual growth leading to perfect strength: by the sacrament of confirmation; the third is spiritual nourishment: by the sacrament of the Eucharist. A fourth remains, which is the spiritual healing; it takes place either in the soul alone through the sacrament of penance; or from the soul flows to the body when this is timely, through extreme unction. These, therefore, bear on those who are propagated and preserved in the spiritual life.
5 Now, those who propagate an! order in the bodily life are marked by two things: namely, natural origin, and t is refers to parents; and the political regime by which the peaceful life of man is conserved, and this refers to kings and princes.
6 It is, then, also like this in the spiritual life. For some propagate and conserve the spiritual life in a spiritual ministry duly, and this belongs to the sacrament of orders; and some belong to the bodily and spiritual life simultaneously, which takes place in the sacrament of matrimony where a man and woman come together to beget offspring and to rear them in divine worship.