II. To the Arguments

43. As to the first argument [n.2] plainly, ‘in a base vow, change the decision’. However, in making the vow one sins mortally.

44. To the next [n.3] I say that, other things equal, the greatest vow is to swear ‘by God’, because by nothing else is it to licit to swear save insofar as God is there in a special way (for instance, ‘by the Gospel’, because God is specially luminous in the Gospel; ‘by heaven’ because God dwells there in a special way; ‘by the Church’, because God is worshipped there in a special way). However, the custom is also reasonable that establishes that certain oaths are made with greater solemnity than others; and about those made with solemnity it is presumed that they are never done without deliberation. Other light oaths can be made without deliberation.     Therefore God and the Church have established, for purposes of fear, that these sort of oaths [sc. ‘by the Gospel’, ‘by heaven’ etc     . Matthew 5.33-37] only be sworn solemnly, and consequently with deliberation and where the truth is to be simply asserted. But oaths ‘by God’ are sworn commonly and lightly, and frequently without deliberation.

45. I say then that, other things being equal, it is a very grave thing to swear ‘by God’. But if there is no deliberation on this side and there is full deliberation on another side, as is the case when an oath is sworn ‘by the Gospel’, there can be mortal sin in the latter case and not in the former - not because of the reverence of him by whom one swears, but because of deliberation in one case and not in the other.

46. And if you object ‘why then does someone who swears by the Gospel become infamous, but not someone who swears by God?’ - I reply that infamy does not always follow the quality of the guilt but the public character of the crime; but it has been established [Gratian Decree, p.2 cause 3, q.9 ch. 20] that an oath be sworn on the Gospel, or be done with deliberation, and that it be public and done publicly. And therefore a transgressor of the oath is presumed to be a violator of the faith, and is reasonably held to be infamous. The same is not presumed about someone else who lightly swears by God falsely.

47. As to the final argument [n.4] it is plain that a promissory oath obligates, but not to fulfilling the act sworn to.