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.

In this chapter, I discuss the preliminary assumptions of the rule-combining approach to morphotactics and advance the two fundamental hypotheses that underlie it: the morphotactic holism hypothesis and the morphotactic variety hypothesis (Section 1.2). In Section 1.3, I review previous proposals that provide empirical support for the morphotactic holism hypothesis, which (unlike the morphotactic variety hypothesis) is not a novel idea. In Section 1.4, I discuss the nature of canonical morphotactics, for which I introduce ten criterial characteristics, construed in rule-based terms. In Section 1.5, I give examples of phenomena that possess these characteristics as well as of phenomena that do not apparently possess them. The morphotactic phenomena to be analyzed in the following chapters deviate from some of these canonical characteristics, but reinforce conformity to others provided that a rule-combining approach is assumed. In Section 1.6, I anticipate the range of topics to be discussed in subsequent chapters.