During the eighteenth and early nineteenth centuries in Germany, psychology grew from a minor branch of philosophical doctrine into one of the central pillars of intellectual culture. In the process psychology's evidential basis, theoretical structure, forms of articulation, and status both as a scientific discipline and as a cultural phenomenon took on a recognisably modern form. It became a fixture in the curricula of German universities, a subject in public and academic debate, and a popular publishing phenomenon, with collections of case histories, journals, and factual and fictionalised life-histories appearing in ever increasing numbers. By the middle of the nineteenth century psychology was – if the pun can be forgiven – institutionalised.

My argument is that the rise of psychology had a significant impact on German literature and thought of the period. Indeed, it is hard to form a historically faithful picture of German intellectual and cultural life without an understanding of psychology's role in it. One of my reasons for writing this book was that students of the philosophy and literature of the period often seem not to appreciate the importance that the writers and thinkers they study attached to psychology. There is a failure, perhaps, to recognise just how aware these early moderns were of a subject that we tend to think of as belonging to our age and not theirs. My argument will be that the eighteenth and early nineteenth centuries had at their disposal some quite sophisticated means of conceptualising psychological states.