The word class preposition contains many highly polysemous members whose meanings may often seem completely unrelated. This project in a close examination of the polysemy network of the German preposition mit in each of the four (documented) major time periods of the language, namely Old High German, Middle High German, Early New High German, and New High German (Penzl 1995). Each of the distinct senses of the preposition is analyzed using Charles Fillmore’s frame semantic approach (Fillmore 1982, Fillmore & Baker 2009, among others) and a visual representation of the polysemy network in each of the time periods is drawn up to show precisely how the senses are related to one another.By using frame semantics as a methodological basis for this undertaking, this work is able to illustrate the motivation behind the changes in the polysemy network diachronically rather than merely appealing to traditional textbook mechanisms of semantic change, such as amelioration, pejoration, synecdoche, etc. (Crowley & Bowern 2010). While these mechanisms are indeed still at work, they do not account for the motivation behind the semantic change. This project aims to offer the field of historical lexical semantics a framework to follow in order to analyze the polysemy network of a word both synchronically and diachronically and to show the motivation behind the semantic changes of that word. This study is organized as follows: In chapter 2, I review traditional, non-cognitive approaches to lexical semantics and illustrate the reasons for which these approaches are ill-suited for the undertaking in this dissertation. Chapter 3 is a discussion of cognitive approaches to lexical semantics and shows the reasons for which I have chosen frame semantics as the theoretical basis for this study. Chapter 4 details the methodology, including discussion of the applicability of frame semantics to this task as well as an overview of the corpora used and the method of data analysis. In chapter 5, I present the findings of this study, including a discussion of the twenty- five frames found in the data to be evoked by the preposition mit as well as visual representations of the synchronic and diachronic polysemy networks of mit. In this chapter, I also compare my findings to three authoritative works which offer semantic analysis of the preposition to varying degrees. In chapter 6, I make concluding remarks, discuss limitations, and suggest further research.