Ludwig Wittgenstein refers to Heinrich Hertz as one of his major influences. However, up to now it was not clear from where he acquired his knowledge of mechanics and in which way it contributed to his philosophy. The aim of this book is to answer these questions. It shows that Wittgenstein came in contact with Hertz’s physical world view during his studies in Berlin. It had an effect on his view of the natural sciences in the Tractatus, and Hertz's conception of mass-particles led to its central notion of a simple object. It was especially Wittgenstein’s teacher in Berlin, Joseph Petzoldt, who played an important intermediary role. The manuscript of his 1907 course of lectures "Grundbegriffe der Mechanik" is published here for the first time. It is complemented by reprints of related texts on the topic by Neumann, Lange and Petzoldt.