Catholic censorship of modern science and natural philosophy in the documents of the Holy Office and Index for Forbidden Books - Leen Spruit Until recently, historical research on the censorial interventions regarding science and natural philosophy by Roman ecclesiastical bodies of doctrinal control focused for the most part on individual cases, such as those of Giordano Bruno and Galileo Galilei. Accordingly, most studies concentrated on the 'victims' of ecclesiastical censorship, rather than on the institutional aspects of the latter. The opening the Roman Archives of the Inquisition and the Index in 1998 permits a more detailed and articulated picture. In my talk I will pay attention to doctrinal and juridical aspects: definition of heresy and heterodoxy, censorship of suspect books (valuation and correction), and in particular the broader views and criteria underlying the ecclesiastical assessment of science and natural philosophy. Analyzing two illustrative cases, heliocentrism (1543-1633) and atomism (1624-1676), I attempt to summarize some effects of censorship.