The motivation for contrastive feature hierarchies in phonology

The notion that phonological features are organized into contrastive hierarchies has been entertained at different times in the history of linguistics. My main focus will be on the motivation for such hierarchies: what principles govern the ordering of the features? I will show that they have been motivated by three different principles: a) Activity: to identify the contrastive features that are relevant to the phonological computation, b) Minimality: to minimize redundancy in phonological representations and to maximize the amount of information conveyed by each feature, and c) Universality: to express universal tendencies in the nature of phonological inventories and the order of acquisition of feature contrasts. These principles do not necessarily conflict in every case, but in practice situations arise where they lead in different directions. To some extent Jakobson and Halle (Jakobson & Halle 1956; Halle 1959) and Clements (2001; 2003; 2009) appeal to all these principles, though they do so with differing emphases: Jakobson began by appealing to Activity, Halle came to stress Minimality, and Clements focused on Universality. I will argue on behalf of the centrality of Activity, which I understand to be the original and most compelling motivation for feature hierarchies.