Heinrich Hertz’s major theoretical treatise, Principles of Mechanics, was one of Wittgenstein’s earliest and longest-lasting influences. Wittgenstein cited Principles twice in the Tractatus, referred to Hertz both times that he gave a public address at Cambridge, and even considered using a quotation from Hertz’s introduction as the motto for the Philosophical Investigations. Furthermore, Wittgenstein once wrote: ‘As I do philosophy, its entire task is to shape expression in such a way that certain worries disappear. ( (Hertz.) )’ Although the significance of Hertz’s influence is generally accepted, Wittgenstein’s specific references to Hertz have not yet been given a detailed interpretation, and so the particular nature of Hertz’s influence on Wittgenstein remains obscure.