by the Jesuit de Benedictis, opposing the views of Descartes, were prohibited with a special condemnation. In 1679, nine years after its publication, was prohibited the treatise by Spinoza entitled _Tractatus theologico-politicus_. This remains on the later Indexes, but as an anonymous work. In the same year were prohibited the _Opera postuma_ of Spinoza which had been printed in Amsterdam, in 1667. The works of Protestant philosophical writers are but sparsely represented in the Index and were probably but little known to the examiners of the Roman Congregation. The names of Leibnitz and Christian Wolff, for instance, do not appear in the Index lists. The Spanish authorities declined to place in their Indexes the works of Descartes, of Malebranche, or of Spinoza. Under the heading of Philosophy, the Indexes of the 17th century contain the names of Montaigne, Charron, Ramus, Bacon, Hobbes, Fludd, and Herbert of Cherbury. In 1709, Hobbes secured the distinction of condemnation in the Roman list for his complete works, of which in the earlier lists only single books had been prohibited. His writings escaped the attention, however, of the Spanish compilers. Julius Caesar Vanini, who was in 1619 burned in Toulouse as a propagator of atheism, and whose name stands in the Spanish Index in Class I, with the specification _Impiissimus atheus_, finds place in the Spanish Index of 1623 only in connection with one work and that with the restriction _d.c._ In the Index of Benedict XIV, the title was repeated but the _d.c._ was cancelled. In the Index of Alexander VII, the natural scientists are, with the noteworthy exception of Galileo, represented only by a few alchemists and a group of physicians. Among the names here to be noted is that of Lionardo di Capua, on the ground of certain sharp criticisms by him of the accepted scholastic philosophy. The name of the mystic Jacob Boehme is not included in any Roman Index but finds place in Class I of the Spanish lists. The prohibition in 1676 of the essays of Montaigne is connected with the specification “in whatever language they may be printed.” The essays of Bacon that received attention from the Roman compilers are the _De dignitate et augmentis scientiarum_ and the _De sapientia veterum_. Sotomayor has entered Franc. Baconus and Franc. Verulam in his first class as two distinct authors. The Spanish Index of 1707 condemns of Bacon _Opera omnia_. The full name, Baron Verulam, appears first correctly in the Spanish Index of 1790. Of the many writings of Robert Fludd (†1637) only one, _Utriusque Cosmi_, etc., appears in the Index. The first work of Thomas Hobbes to receive attention was the _Leviathan_, prohibited in 1703, about forty years after its publication. In 1709, however, thirty years after the author’s death, the prohibition was made to include the _Opera omnia_.