As the only book-length general history and defense of energetics, Georg Helm's Energetik is a unique and important work. Conceived in the strife of the great debate on energetics at the Lubeck Naturforscherversammlung, Helm's book seeks to achieve several distinct, although often closely related, objectives. It tries to revise, clarify and defend Helm's own development of energetic theory in order to rebut critics, especially Boltzmann and Planck. It also seeks to defend and promote a phenomenalist conception of energetics and thus a view of the history, nature and goal of physical theory that both responds to criticism and separates Helm's vision of a science of energy from those of others, notably Ostwald. Finally, it presents and defends energetics, despite its fitful development, as 'a unified development of thought', which must be 'understood as a whole', since it amounts to nothing less than a 'great reorientation in the human understanding of natural events'. This book provides the first English translation of Helm's seminal work and offers an introduction to its contours and content.