2. According to the opinion now almost universally received, this necessity does not exist—so far as the validity of the dispensation is concerned—except when the gradus propior is the gradus primus, which should be always mentioned, whether it concurs with the second, third, or fourth; and your correspondent is quite correct in stating that a misapprehension of the meaning of a constitution of Benedict XIV. has led St. Liguori to adopt an opinion completely at variance with this. But it is manifest that the Saint's mistake has not been "inserted in the very latest editions of the works on moral theology most in use at present—such as those of Gury and Scavini"; for, while St. Liguori extends the necessity to all those cases in which the first or second degree concurs with another more remote (Theol. Mor., lib., n. 1136), Gury falls into the opposite extreme by maintaining that in consanguinitate inaequali, even the first degree need not be mentioned, except when it concurs with the second (Gury, Theol. Moralis, 13th ed., p. 594, n. 867, not 876.)
3. Scavini certainly copied in the earliest editions of his work the opinion of St. Liguori; but the mistake has been long since corrected. In the Paris Edition of 1855, he says: "Declaravit Benedictus XIV., Brevi Etsi, conjugium ... illicitum esse sed non invalidum modo propinquitas non sit primi gradus consanguinitatis vel affinitatis, scilicet mixti cum caeteris usque ad quartum gradum"—t. 4, p. 503. I have examined several editions which were published since the one from which I have quoted, and in all these the same view is laid down.
4. Your correspondent states that the opinion of Gury was adopted by Scavini. I think this statement is hardly correct. Most certainly it is not correct with reference to any of the editions of Scavini's works which are commonly used in Ireland.
5. In a late edition of Gury's work, which, I suppose, has not yet fallen under the notice of your correspondent, the error in n. 867 is corrected by the following note: "Invalidatur in genere, dispensatio si reticetur primus gradus ... pro foro interno, expressio propioris gradus non requiritur nisi sit primus". Editio tertia Germanica n. 867, p. 465.
6. Cardinal Gousset undoubtedly followed the view of St. Liguori; but the reference to his work should be t. 2, n. 865, not n. 1136.
7. In conclusion, I may remark that the theory suggested by your correspondent as a possible explanation of St. Liguori's mistake, does not appear to be admissible. The constitution Etsi Matr. had reference indeed to a case in which two impediments existed; and the Pope declared that the marriage was invalid, because no mention had been made of the double impediment in the petition for the dispensation. He explained, however, at some length that the invalidity was caused by this defect alone, and that no difficulty would have arisen in case there had been but one impediment—relationship in the third and fourth degrees, although the dispensation had been granted for the fourth without any mention of the third.
Amongst other reasons for this decision, he speaks of the common consent of theologians, who agree that in the case of a relationship in the third and fourth degrees, it is not necessary to mention the gradus propinquior when seeking the dispensation.
There can be no doubt that it was this passage which induced St. Liguori to conclude that if the gradus propinquior were the first or second, it should be expressed in the petition.
He could hardly have committed such a mistake as to suppose that duplex impedimentum, meant an impediment of consanguinity in the second degree. It is evident that he did not fall into this error, for immediately afterwards, when discussing the question regarding a duplex impedimentum (n. 1138), he adopts the opinion of Benedict XIV. on this subject, quoting the same constitution, Etsi, in support of his view.