And indeed The Genealogy of Morals ends by questioning the search for truth, describing it as the last remnant of Christian asceticism, and speaking admiringly of the Islamic sect whose secret doctrine was 'Nothing is true, everything is permitted' (III, 24). Hence there could be no literal language, because there would be no solid reality for such language to refer to. Where, though, does metaphor stop and literal meaning begin? Many of Nietzsche's recent interpreters ascribe to him a radical epistemological skepticism that would deny the possibility of knowledge and truth. His constant reference to these sciences gives Nietzsche's late prose a rich metaphorical texture. In addition, especially in the third essay, he appeals also to physiology and medicine. One is philology, which traces the transformation of words the other is evolutionary biology, which examines the transformation of organisms. Nietzsche therefore needs models for change combined with continuity, and he finds two such models in the sciences of his own day. But it also undertakes to reveal the continuity, for instance, between the early priest with his terrifying ascetic practices and the modem scholar whose asceticism takes the form of a devotion to truth. It asks, for example, how primitive man, who lived from day to day, was changed, over the millennia, into the modern autonomous subject capable of remembering the past and making promises about the future. Being concerned with origins, it is also concerned with change and continuity. It undertakes to explain the origins not only of morals but of society, custom, law, class differences, religion, priesthood, and scholarship-all under the sign of the Will to Power. Nietzsche's Genealogy of Morals is a hugely, almost insanely ambitious treatise.

At certain difficult points in Nietzsche's argument, these metaphors come under strain, especially when Nietzsche applies a whole series of incompatible metaphors to explain (or seem to explain) the development of 'slave morality.' To test this insight, the present article examines particularly the metaphors (or apparent metaphors) used for processes of change in The Genealogy of Morals, showing how Nietzsche draws on two branches of scholarship that he especially valued: philology and biology. But recent studies suggest that Nietzsche worked within a nineteenth-century intellectual context that may be called 'biologism,' which saw biology as providing models for processes in other areas of life, but did not reduce them to biology. Recent commentators, anxious to avoid biological reductionism, have interpreted such terms as purely metaphorical. But the boundaries between metaphor and literal language are unclear, especially when Nietzsche uses biological terms. It is a commonplace that Nietzsche makes heavier use of metaphor than most philosophers.

Darwin master slave morality