The project is situated within the field of philosophy of biology or bio-philosophy, and more specifically the bio- philosophy of evolutionary theory and Darwinism. We will investigate the theoretical and empirical conditions for evolution by Darwinian natural selection versus Lamarckian instruction. The latter, ‘pre-Darwinian’ hypothesis on biological evolution is currently taken back into consideration in contemporary evolutionary systems biology. We will analyse its conceptual and empirical relationship to natural selection as well as the crucial heuristic role the Weismann barrier plays in this.