To become an historian was already my aim in the last forms of the gymnasium, prior to 1914, though I hardly knew anything about the profession. My father, an attorney, had been thinking of me as of his successor, yet tolerance was one of his outstanding traits. He was willing to wait until the full development of my capacities, the more so since history had always been one of his major interests. My gymnasium — perhaps even more than other Berlin gymnasia — stressed German and especially Prussian history. Even teachers with a wider horizon, such as Wilhelm Pfeifer who had been one of the last amanuenses of Ranke, were obliged to emphasise Prussian history. I remember that one whole semester was given over to the campaigns of Frederick the Great. Pfeifer was a thoughtful and independent teacher, well above the level of his colleagues. I stayed in contact with him until I left Germany in 1935. Later my American students thought that, by way of Pfeifer, Ranke's blessing had been bestowed on me — a kind of successio apostolorum.

In the year prior to my graduation from the gymnasium I learnt that recently a book of a new type of history had appeared in the form of Friedrich Meinecke's Weltbuergertum und Nationalstaat. I read it, and it was this book which led to my decision to study history. By showing the influence of cosmopolitan concepts on the emergence of the German national idea Meinecke's book opened up a new historical dimension, the history of ideas — not without objection from other historians that he neglected “real” history.