xl INTRODUCTION TO VOLUME 1 role also played on occasion by his friends Michele Besso and Conrad Habicht. Until now, scholars have been almost entirely dependent on later reminis- cences by Einstein and others for evidence of his intellectual preoccupations during these years. The new documents often confirm such reminiscences, with the immediacy of a contemporary account and a wealth of detail. In addition, they reveal some previously unknown early interests, such as Einstein's concern with thermoelectricity, with Drude's electron theory of metals, and with the spectral properties of matter. Although Einstein was personally isolated from the scientific community at this time, he kept abreast of the most important developments in physics through the Annalen der Physik. His choice of articles to discuss in his let- ters already shows his intuition for the "Fundamental-Wichtige" in physics (Einstein 1979, p. 14). Soon after their appearance, he read Planck's papers on black-body radiation, Drude's papers on the electron theory of metals, Wien's report on attempts to detect the translatory motion of the ether, and a paper by Lenard on the photoelectric effect. Near the end of his life Einstein recalled that work on the special theory of relativity "had been his life for over seven years and that this was the main thing" (Shankland 1963, p. 56). Doc. 52 establishes that, in mid-1899, Einstein was deeply interested in the electrodynamics of moving bodies and expressed skepticism about attributing a state of motion to the ether. An editorial note preceding this letter traces the discussion of this theme in his letters. Einstein also started work on a theory of thermoelectricity in 1899. He was familiar with Planck's studies of radiation by early 1901 and soon attempted to apply Planck's resonator concept to an understanding of the thermal properties of solids. Einstein's comments on electrical, thermal, and radia- tion phenomena, and their relationships, are reviewed in an editorial note preceding Doc. 58. In 1900 Einstein worked out a theory of molecular forces, which he applied to liquids. He tried to extend his theory to gases and submitted a dissertation on the subject in 1901, which he apparently withdrew early in 1902. Einstein's work on molecular forces led to his interest in the foundations off thermody- namics. These two topics were the subject of his first three publications, all conceived during the period covered by this volume. An editorial note preceding Doc. 79 provides an overview of his work on molecular forces. In discussing such topics, Einstein constantly tried to relate different and sometimes apparently disparate physical phenomena, employing an atomistic conception of the nature of matter and of electricity. He eagerly pursued the