the doctrine and science of conscience and its cases, with the rules and principles of resolving the same; drawn partly from natural reason or equity; partly from authority of scripture, the canon law, councils, fathers, &c. To casuistry belongs the decision of all difficulties arising about what a man may lawfully do or not do; what is sin or not sin; what things a man is obliged to do in order to discharge his duty, and what he may let alone without breach of it.

CASIUS AMMISSIONIS, in Scots law, in actions proving the tenor of obligations inextinguishable by the debtors retiring or cancelling them, it is necessary for the pursuer, before he is allowed a proof of the tenor, to condescend upon such a casus ammissionis, or accident, by which the writing was destroyed, as shows it was lost while in the writer's possession.