This volume contains the collected works of the chemist and physicist Lars Onsager, one of the most influential scientists in the 20th century. It includes in addition a biography by H.C. Longuet-Higgins and M.E. Fisher, an autobiographical commentary, selected photographs and a list of Onsager discussion remarks in print. Onsager's scientific achievements were characterized by deep insights into the natural sciences. His two best-known accomplishments are his reciprocal relations for irreversible processes, for which he received the 1968 Nobel Prize in Chemistry, and his explicit solution of the two-dimensional Ising model, a mathematical "tour de force" that created a sensation when it appeared. In addition, he made significant theoretical contributions to other fields, including electrolytes, colloids, supercondctivity, turbulents, ice, electrons in metals, and dielectrics. In this volume Onsager's contributions to the different scientific fields are evaluated by leading experts. The commentatrors are P.W. Anderson, R. Askey, A. Chorin, C. Domb, R.J. Donnelly, W. Ebeling, H.N.W. Lekkerkerker, P. Mazur, H. McKean, J.F. Nagle, T. Odijk, A.B. Pippard, G. Stell, G.H. Weiss and C.N.
Yang.