Abstract: The term 'change' is used to refer to a number of different processes in Linguistics including: imperfect acquisition leading to a difference between the grammar of parent and their child, the altering of a grammar over the course of a speaker's life, and the spread of an innovative form through a community. The Historical Linguistic literature often fails to distinguish these events, discussing the 'spread of a novel grammar' as if the grammar itself is passed from person to person or even, addressing historical change as developmental steps in the evolution of a Language (e.g. French, English, Swahili) as if it were a homogenous organism choosing to change. Thus, historical work often progresses without a theory of change. Here, I discuss which definition of 'change' is assumed in various types of Historical Linguistic study and whether Historical Linguists can be said to study it at all.