Rules of Conscience and the Case of Galileo
Rudolf Schüssler

Galileo’s (in)famous trial has been scrutinized from many perspectives, but its relation to scholastic casuistry did not receive much attention. This is unfortunate, since scholastic attempts to regulate consciences and to formulate an ethics for certain sciences can throw light on important details of the Galileo affair. New doctrines of moral judgment, like scholastic probabilism (founded 1577), may partly account for the Church’s reluctance to admit the rational acceptability of Copernicanism. Probabilism was one of the most challenging developments in early modern casuistry. Galileo himself, as it seems, tried to benefit from casuistical strategies of argumentation. Scholastic casuistry, however, included codes of conduct for potentially ethically problematic sciences like medicine and law. Since in many Catholic eyes Copernican astronomy implied ethical hazards, the ethical regulation of astronomical research seemed appropriate. But Galileo became the paradigm of a modern scientist – by not allowing to regulate his conscience. Whether or not one accepts this result, my paper should at least show that knowledge of scholastic casuistry is important for understanding the intricacies of the Galileo affair.