Contents: Introduction; Part I Function and Purpose in Biology: Functions as selected effects: the conceptual analyst's defense, Karen Neander; A modern history theory of functions, Peter Godfrey-Smith; Function without purpose: the uses of causal role function in evolutionary biology, Ron Amundson and George V. Lauder; Function, homology and character individuation, Paul E. Griffiths. Part II Adaptionism, Optimality and Adaptive Co-Variation: Adaptationism and the power of selection, Peter Godfrey-Smith; Optimality models and the test of adaptionism, Steven Hecht Orzack and Elliott Sober; Testing adaptationism: a comment on Orzack and Sober, Robert N. Brandon and Mark D. Rausher; The causes of natural selection, Michael J. Wade and Susan Kalisz. Part III Fitness, Drift and the Forces of Evolution: The propensity interpretation of fitness, Susan K. Mills and John H. Beatty; Chance and natural selection, John Beatty; The indeterministic character of evolutionary theory: no 'no hidden variables proof' but no room for determinism either, Robert N. Brandon and Scott Carson; Is indeterminism the source of the statistical character of evolutionary theory?, Leslie Graves, Barbara L. Horan and Alex Rosenberg; Are random drift and natural selection conceptually distinct?, Roberta L. Millstein; The trials of life: natural selection and random drift, Denis M. Walsh, Tim Lewens and Andre Ariew; Fitness, probability, and the principles of natural selection, Frederic Bouchard and Alex Rosenberg. Part IV Selfish Genes, Altruistic Organisms and the Levels of Selection Debate: Reviving the superorganism, David Sloan Wilson and Elliott Sober; The return of the group, Kim Sterelny; The 'averaging fallacy' and the levels of selection, Samir Okasha; The empirical nonequivalence of genic and genotypic models of selection: a (decisive) refutation of genic selectionism and pluralistic genic selectionism, Robert N. Brandon and H.Frederik Nijhout. Part V Three Challenges from Development