As this book unfolds, we will see that the verbs of the Athapaskan family exhibit two attributes, outlined in chapter 1. First, global uniformity exists – morpheme order is similar across the family. Second, so does local variability – some variability in morpheme order occurs both within a language and across the family. In this chapter I examine some possible hypotheses to account for both of these properties.

Two Hypotheses

One can imagine different ways of accounting for the fact that the Athapaskan language family as a whole exhibits both global uniformity and local variability. I outline two here. Under both hypotheses, global uniformity has its origins in the languages having a common source, but they differ as follows. Under one hypothesis, it is the common source and history of the languages that accounts for the global uniformity. It is an accident of history that certain properties remained stable across the language family while others were subject to change within individual languages. I call this the template hypothesis. Under a second hypothesis, global uniformity finds its origins in the languages having a common source, but results additionally from principles of universal grammar, which might be either diachronic or synchronic. I call this the universal or scope hypothesis.

In this chapter I examine why certain aspects of verb morphology are invariant while others have been susceptible to change, both across languages and within a particular language.