The high percentage of works on this theme reflects the fact that, after classical antiquity, Christianity became the predominant power shaping European culture between the 13th and 19th centuries. Biblical texts, commentaries, and apocryphal stories inspired artists and patrons alike to create these objects of devotion, yet the translation of the Word into paint often raised difficult problems. 
Artists and their advisors were faced with the challenge of suggesting, in visual terms, the nature of Christian mysteries – such as the visions experienced, or miracles performed, by the saints – as well as other profound theological beliefs and debates.
These images were made to inspire and strengthen faith through public and private devotion in churches or domestic settings. (from the National Gallery)