In his choice of texts, the Editor has been faced with the difficult task of selecting, from among the author's more than 600 publications, those of the greatest philosophical interest. It is chiefly the topics of value-rela tivism and the logic of norms that have been kept in view. The selection has also been guided by the endeavour to reprint, so far as possible, texts which have not hitherto appeared in English. At times, however, this aim has had to be discarded, in order to include works of key im portance and also the latest expressions of Kelsen's view. In addition to the two topics...