I answer that, When we compare things in the point of super-eminence, we look not at that in which they agree, but at that wherein they differ. Now in parish priests and archdeacons three things may be considered, their state, their order, and their office. It belongs to their state that they are seculars, to their order that they are priests or deacons, to their office that they have the cure of souls committed to them.
Accordingly, if we compare these with one who is a religious by state, a deacon or priest by order, having the cure of souls by office, as many monks and canons regular have, this one will excel in the first point, and in the other points he will be equal. But if the latter differ from the former in state and office, but agree in order, such as religious priests and deacons not having the cure of souls, it is evident that the latter will be more excellent than the former in state, less excellent in office, and equal in order.
We must therefore consider which is the greater, preeminence of state or of office; and here, seemingly, we should take note of two things, goodness and difficulty. Accordingly, if we make the comparison with a view to goodness, the religious state surpasses the office of parish priest or archdeacon, because a religious pledges his whole life to the quest of perfection, whereas the parish priest or archdeacon does not pledge his whole life to the cure of souls, as a bishop does, nor is it competent to him, as it is to a bishop, to exercise the cure of souls in chief, but only in certain particulars regarding the cure of souls committed to his charge, as stated above (Article [6], ad 2). Wherefore the comparison of their religious state with their office is like the comparisons of the universal with the particular, and of a holocaust with a sacrifice which is less than a holocaust according to Gregory (Hom. xx in Ezech.). Hence it is said (XIX, qu. i, can. Clerici qui monachorum.): "Clerics who wish to take the monastic vows through being desirous of a better life must be allowed by their bishops the free entrance into the monastery."
This comparison, however, must be considered as regarding the genus of the deed; for as regards the charity of the doer it happens sometimes that a deed which is of less account in its genus is of greater merit if it be done out of greater charity.
On the other hand, if we consider the difficulty of leading a good life in religion, and in the office of one having the cure of souls, in this way it is more difficult to lead a good life together with the exercise of the cure of souls, on account of outward dangers: although the religious life is more difficult as regards the genus of the deed, by reason of the strictness of religious observance. If, however, the religious is also without orders, as in the case of religious lay brethren, then it is evident that the pre-eminence of order excels in the point of dignity, since by holy orders a man is appointed to the most august ministry of serving Christ Himself in the sacrament of the altar. For this requires a greater inward holiness than that which is requisite for the religious state, since as Dionysius says (Eccl. Hier. vi) the monastic order must follow the priestly orders, and ascend to Divine things in imitation of them. Hence, other things being equal, a cleric who is in holy orders, sins more grievously if he do something contrary to holiness than a religious who is not in holy orders: although a religious who is not in orders is bound to regular observance to which persons in holy orders are not bound.
