The paper argues in favour of a reductionist strategy in the philosophy of biology in order to maintain the unity of science. After considering the problems in the current state of the philosophy of science that beset both the anti-reductionist and reductionist camps, I design a conservative, non-eliminativist, alternative reductionist strategy based on the theoretical possibility of constructing functionally defined sub-concepts in biology that are nomologically coextensive with physical descriptions. This theoretical link between biology and physics makes it possible to understand the original and operational biological concepts as abstractions from these biological sub-concepts. Thus, in a sense, we can 'serve two masters', preserving the fundamental role of physics while allowing biology its proper sphere of explanatory autonomy, and thus its scientific character. Since this abstraction step is an intra-theoretic one, the scientific quality of the original biological concepts can be vindicated because both epiphenomenalism and eliminativism are avoided, a result that is not available in standard reductionist or antireductionist approaches. Against this background, we can argue furthermore that biological kinds are natural ones and that biology adumbrates laws and explanations of different degrees of abstraction. * Special thanks to Michael Esfeld, Patrice Soom, the participants of the workshop on "Reduction, explanation and metaphors in the philosophy of mind" (Bremen, September 2009), those of the "European advanced seminar in philosophy of life science" (Geneva, September 2010) and the anonymous reviewer for constructive comments on this paper.