Fruitful interaction between historical linguistics and linguistic theory is rarely the aim and even more rarely achieved ... Allen's work is a remarkable exception. It is her avowed intention to bring together the methodology, assumptions and principles of the two disciplines, to show that each can benefit from the other. This she does with signal success. Allen presents a careful and detailed examination of changes in case marking and claimed relationships to syntactic changes. This in itself is valuable and significant. More investigation ... a rewarding blend of descriptive rigour and theoretical insight.