In the spring of 1919, two British solar eclipse expeditions confirmed the correctness of general relativity theory and propelled Albert Einstein to instant celebrity. Before this major turning point, the majority of Einstein's writings published in this volume dealt with the clarification of general relativistic problems, such as the status of the metric field, the character of gravitational waves, the problem of energy-momentum conservation, and questions of cosmology, such as the nature and size of the universe and the distribution of matter within it. After his rise to international fame, Einstein's publications changed markedly. He faced an increasing demand for popular articles and lectures on relativity, its development and meaning. He also felt compelled to respond to a host of commentators, ranging from skeptical physicists to philosophers trying to reconcile his revolutionary theory with their views. For the first time, he also responded in print to outspoken anti-relativists, some of them fueled by cultural conservatism and, frequently, anti-Semitism.
Einstein used his newly won fame to lend prestige to political causes, especially to the reconciliation among European nations and to Zionism. In the early years of Weimar Germany, Einstein spoke out vigorously for the young republic, emphasizing the rights of the individual. He agonized over the misery of the Central Europeans in the grip of starvation and economic collapse, praised the support of individuals and groups such as the Quakers, and championed the cause of Eastern European Jews. His rejection of assimilation, combined with a fierce defense of the right of Jews to higher education, led Einstein to campaign for the establishment of a university in Palestine, the land which he conceived of as a cultural center for all Jews.