Trait X is fitter than trait Y in a population of organisms if those organisms have other biological traits T and live in an environment that has properties E. The theory of natural selection is filled with statements of this form.
Elliott SoberThe indispensability argument says (roughly) that if you have ample reason to accept an empirical scientific theory that makes indispensable use of mathematics, and that theory entails that numbers exist, then you have ample reason to accept that numbers exist. The argument affirms the antecedent of this conditional, and concludes that you have ample reason to believe that numbers exist. What is striking about this argument is that it seems to show that the empirical reasons that suffice for accepting a scientific theory also suffice for accepting a metaphysical claim.
Elliott SoberIt can be a necessary conceptual truth that pains are painful without this ruling out the physicalist thesis that immaterial minds are impossible or the thesis that conscious states supervene on physical states. The necessity involved in these claims is nomological necessity, not metaphysical necessity (assuming that these are different).
Elliott SoberPhilosophers of biology generally recognize that evolutionary fitness (roughly, an organism's ability to survive and reproduce in its environment) is multiply realizable.
Elliott SoberEvolutionary theory, properly understood, does not conflict with the idea that God occasionally intervenes in nature - for example, by once or twice causing a beneficial mutation to occur. Biologists have not detected any such interventions despite the data and theory they have assembled about mutation. However, I think it is a mistake to expect biological experiments to be able to detect such one-off acts of divine intervention, especially if those acts occurred in the distant past. Science isn't in that line of work.
Elliott Sober