Languages often present cases in which two rules together express content some of which cannot be attributed to either rule individually. The inflection of regular verbs in Breton presents several examples of this sort; holistic rule combinations are a way of modeling this phenomenon. Some instances of holistic combination have an emergent character; these are cases in which all of the forms realized by the composite of two rules happen to possess a property P that neither rule realizes on its own. In such cases, the composite is open to reanalysis as a holistic combination realizing P. Limbu verb morphology provides an example of this sort. A particularly compelling case for the postulation of holistic combinations arises in systems in which the same two rules express different holistic content in different contexts; Old English verb inflection is a system of this sort.