[Footnote 117: _1st. del Conc. Trid_. vol. ii. p. 91. The passage deserves to be Paul IV. designated in his transcribed. 'Sotto colore di fede e religione sono vietati con la medesima severita e dannati gli autori de'libri da'quali l'autorita del principe e magistrati temporali e difesa dalle usurpazioni ecclesiastiche; dove l'autorita de' Concilj e de'Vescovi e difesa dalle usurpazioni della Corte Romana; dove le ipocrisie o tirannidi con le quali sotto pretesto di religione il popolo e ingannato o violentato sono manifestate. In somma non fu mai trovato piu bell'arcano per adoperare la religione a far gli uomini insensati.'] Index Expurgatorius sixty-one printing firms by name, all of whose publications were without exception prohibited, adding a similar prohibition for the books edited by any printer who had published the writings of any heretic; so that in fine, as Sarpi says, 'there was not a book left to read.' Truly he might well exclaim in another passage that the Church was doing its best to extinguish sound learning altogether.[118] In order to gain a clear conception of the warfare carried on by Rome against free literature, it will be well to consider first the rules for the Index of Prohibited Books, sketched out by the fathers delegated by the Tridentine Council, published by Pius IV., augmented by Sixtus V., and reduced to their final form by Clement VIII. in 1595.[119] Afterwards I shall proceed to explain the operation of the system, and to illustrate by details the injury inflicted upon learning and enlightenment. [Footnote 118: _Discorso Sopra l'Inq._ vol. iv. p. 54.] [Footnote 119: These rules form the Preface to modern editions of the Index. The one I use is dated Naples, 1862. They are also printed in vol. iv. of Sarpi's works.]