Can "ought" be derived from "is"? This text presents a systematic investigation of this time-honoured philosophical problem by means of modern alethic-deontic predicate logic. Two comprehensive introductory chapters into the philosophical and logical foundations make the text understandable for non-logicians, ethicists, social scientists and students of philosophy. New in this study are two topics: relevance and metalogical generality. It turns out that "is-ought" inferences indeed exist, but they are all irrelevant in a precise logical sense. New proof techniques allow the establishment of this result for very broad classes of logics. A profound philosophical investigation of the question of analytical or strongly intersubjective is-ought bridge principles supplements the logical study. The final results imply incisive limitations for the justifiability of ethics as opposed to empirical science.
`... anyone interested in deontic logic should benefit from the insights of this book. ... the work is clearly written and excellently edited.'
History and Philosophy of Logic, 19 (1998)