Developmental biology, as a science, is full of mystique. My imagination was easily captured by the amazing journey of the organism from egg to adult, the robustness of development under variable conditions, and the remarkable emergence of complexity during ontogeny. The project of understanding development is one taken up by philosophers of biology only recently, despite having its roots in Aristotle, and I suspect one of the reasons is that development has always been shrouded in a tapestry woven of vitalistic strands so long anathema to philosophers working on the natural sciences.

In the main, philosophers of biology have tended to sidestep development; they have, instead, tended to analyse the apparently more tractable problems of evolutionary biology (particularly fitness) and, more recently, molecular biology and genetics (particularly the relation between classical and molecular genetics). There are, of course, exceptions to these tendencies. In fact, a growing number of philosophers of biology are now exploring the complexities of development. This book catalogues some of the most interesting aspects of this philosophical work, in the context of a sustained introduction to recent developmental science and theory.

In the following pages, I offer a philosophical account of organismal development, address the character of developmental mechanisms, and argue that we should resist the assumption that development can be explained exclusively in terms of gene action and activation.