The name "False Decretals," or "Decretals of the Pseudo-Isidore," is given to certain apocryphal papal letters contained in a collection of canon laws composed about the middle of the ninth century by an author who employs the pseudonym of Isidore Mercator. The forged letters number about one hundred, and many fragments of them found their way into the "Corpus Iuris Canonici." Their chief purpose was to win respect for the Episcopal authority, not to increase the power of the papacy, as Protestants have claimed. There is a good account of the whole matter in Vol. V of the Catholic Encyclopedia. But we have hitherto lacked a satisfactory English treatise in book form. This need has now been supplied by Mr. E. H. Davenport, a non-Catholic lawyer, whose book on "The False Decretals" (Oxford: Blackwell), according to the :Catholic Book Notes" (London, No. 225, p. 82), is "the most complete answer to the common Protestant calumny about the influence of the False Decretals on the papacy that could be desired by any Catholic apologist."
Mr. Davenport's conclusions are summarized by our esteemed contemporary as follows:--
The forged texts fall into three classes--defensive, against aggression of the State in Church matters; constructive, about the administration of Church authority; aggressive, which, if urged, would lead to the supremacy of the Church over the State. Pseudo-Isidore is in no way concerned to magnify the papal office--indeed, in one point, his desire to restore primates is rather against the papacy. Nor does' he make anything of the "Donatio Constantini." His chief objects are defence of bishops and priests, and attacks on chorepiscopi and metropolitans. In no point was his work of any influence till the eleventh century. As far as the popes are concerned, they did not use the False Decretals, because they did not need them; there were already plenty of authentic documents from which they could quote. Thus Nicholas I and Adrian II quote decrees of former popes, not according to Pseudo-Isidore, but from authentic sources. "The False Decretals were based upon ancient custom: so were the doctrines of papal supremacy: there was no need for them to be based on the False Decretals" (p. 57). It was only in the eleventh century, when the Church had already established all the rights that Pseudo-Isidore gives her, that he begins to be quoted as confirming what was already known....
--The Fortnightly Review, Volume 24 [1917]