In the gradual work of definition professional jurists played only a belated and, on the whole, insignificant part. It is true that, as early as about 1020, Bishop Fulbert of Chartres, whose study of the canon law had trained him in the methods of legal reflection, attempted an analysis of homage and its effects. But interesting though it was as a symptom of the penetration of jurisprudence into a sphere which had hitherto been alien to it, this endeavour scarcely succeeded in rising above the level of a rather barren scholastic exercise. The decisive influence, here as elsewhere, was that of custom, formed by precedents and progressively crystallized by the legal practice of courts attended by many vassals. More and more frequently, the practice was adopted of having these stipulations, which but a short while before had been purely traditional, included in the agreement itself. The oath of fealty, since it could be expanded at will, formed a better vehicle for the details of these conditions than the few words that accompanied the act of homage. Thus a detailed contract, carefully drawn up, replaced
an unqualified submission. As a further precaution, which clearly testifies to the weakening of the tie, the vassal as a rule no longer promised merely to render aid to his lord. He was now required in addition to undertake not to injure him. In Flanders, from the beginning of the twelfth century, these negative clauses had assumed sufficient importance to give rise to a separate oath of ‘security’ which was sworn after fealty and apparently authorized the lord, in the event of the vassal’s failure to observe it, to distrain on certain specified pledges. It goes without saying, however, that for a long time it was the positive obligations which continued to hold first place.