Question II. On the Virtues of Piety, Observance, and Obedience, or on the Fourth Precept of the Decalogue

568. Order of matters to be treated. After discussion of the noblest potential part of the virtue of justice, namely, the virtue of religion and the vices opposed to it, it remains (following the footsteps of the Angelic Doctor) to treat the remaining potential parts of justice, namely, piety, observance, obedience, gratitude, vindication, truth, affability, liberality, and epikeia. Sufficient has already been said above, n. 165ff., concerning truth or truthfulness, when there was discussion of lying. Therefore the other virtues remain to be explained, concerning which treatment will be given in two parts, namely: 1. on piety, observance, and obedience; 2. on gratitude, vindication, affability, liberality, and epikeia. The reason for this subdivision is that the first three virtues include nearly those things which are established in the fourth precept of the Decalogue, and thus, after the explanation of the first three precepts of the Decalogue made in the preceding tract, the explanation of the fourth precept fittingly follows.

It is expedient to treat separately these virtues (piety, observance, and obedience) in general and the same virtues insofar as they must be observed by children, parents, subjects, superiors, etc. For thus an occasion is also furnished for discussing the duties of certain states, since there is no special tract on the states of men in this Manual.