Thirdly, because a vow fixes the will on the good immovably and to do anything of a will that is fixed on the good belongs to the perfection of virtue, according to the Philosopher (Ethic. ii, 4), just as to sin with an obstinate mind aggravates the sin, and is called a sin against the Holy Ghost, as stated above (Q. 14, A. 2).
Reply Obj. 1: The passage quoted should be understood as referring to necessity of coercion which causes an act to be involuntary and excludes devotion. Hence he says pointedly: "Lest that which we are free to do be done without devotion and unwillingly." On the other hand the necessity resulting from a vow is caused by the immobility of the will, wherefore it strengthens the will and increases devotion. Hence the argument does not conclude.
Reply Obj. 2: According to the Philosopher, necessity of coercion, in so far as it is opposed to the will, causes sorrow. But the necessity resulting from a vow, in those who are well disposed, in so far as it strengthens the will, causes not sorrow but joy. Hence Augustine says (Ep. ad Arment. et Paulin. cxxcii): "Repent not of thy vow: thou shouldst rather rejoice that thou canst no longer do what thou mightest lawfully have done to thy detriment." If, however, the very deed, considered in itself, were to become disagreeable and involuntary after one has taken the vow, the will to fulfil it remaining withal, it is still more meritorious than if it were done without the vow, since the fulfilment of a vow is an act of religion which is a greater virtue than abstinence, of which fasting is an act.
Reply Obj. 3: He who does something without having vowed it has an immovable will as regards the individual deed which he does and at the time when he does it; but his will does not remain altogether fixed for the time to come, as does the will of one who makes a vow: for the latter has bound his will to do something, both before he did that particular deed, and perchance to do it many times. _______________________
SEVENTH ARTICLE [II-II, Q. 88, Art. 7]
Whether a Vow Is Solemnized by the Reception of Holy Orders, and by the Profession of a Certain Rule?
Objection 1: It would seem that a vow is not solemnized by the reception of holy orders and by the profession of a certain rule. As stated above (A. 1), a vow is a promise made to God. Now external actions pertaining to solemnity seem to be directed, not to God, but to men. Therefore they are related to vows accidentally: and consequently a solemnization of this kind is not a proper circumstance of a vow.
Obj. 2: Further, whatever belongs to the condition of a thing, would seem to be applicable to all in which that thing is found. Now many things may be the subject of a vow, which have no connection either with holy orders, or to any particular rule: as when a man vows a pilgrimage, or something of the kind. Therefore the solemnization that takes place in the reception of holy orders or in the profession of a certain rule does not belong to the condition of a vow.
Obj. 3: Further, a solemn vow seems to be the same as a public vow. Now many other vows may be made in public besides that which is pronounced in receiving holy orders or in professing a certain rule; which latter, moreover, may be made in private. Therefore not only these vows are solemn.
On the contrary, These vows alone are an impediment to the contract of marriage, and annul marriage if it be contracted, which is the effect of a solemn vow, as we shall state further on in the Third Part of this work [*Suppl., Q. 53, A. 2].