Peter Lombard: (c.1100-1160) As theologian and teacher, Peter Lombard, also called Peter the Lombard, was best known for his Book of Sentences. This major piece of work explained Christian dogma in an easily understood style, including discussions on the Trinity, creation, sin, sacraments and incarnation. Lombard's work, while mostly theologica l in nature, often ran against several of Gratian's teachings in canon law. Even though both men were trying to improve Christians' religious understanding by simplifying theological sources, they actually succeeded in splitting up church leaders into philosophical and canonical camps.

One specific area in which Lombard differed from Gratian was in regard to what made a marriage valid. Lombard required that there were words of the future, (betrothal) words of the present (saying "I do") and c onsummation, as opposed to Gratian's prerequisites of consent, affection, and consummation. Because Lombard enjoined that words of the present, verba de praesenti, needed to be said, not just betrothal, to make a marriage valid, it was not as acceptable to casually have sex if one promised to marry one's partner. The significance this had for the family was that Lombard's interpretation made clandestine marriages the same as fornication.--Jessica Steyler