This project aims to provide a new theoretical understanding of the nature of the organism. Taking the machine conception of the organism as its critical target, the project will elaborate an ontological conception of life that highlights its intrinsically purposive self-maintaining organization. It will also consider the implications that such non-mechanical—yet scientifically-grounded—understanding has for how living systems should be studied and explained, and more generally for how the epistemic relation between biology and the physical sciences should be construed. This novel philosophical outlook on organisms will be developed by drawing on a virtually forgotten school of biological thought known as ‘organicism’, which came to prominence between the First and Second World Wars, but which subsequently became marginalized following the rise of molecular biology. By revisiting the organicist tradition and updating its core ideas, the project will not only reshape current theoretical views regarding the nature of life, but also restore organisms to their rightful place in the edifice of biological theory. In the process of doing so, the organism-centred perspective developed in the project will be used to address a number of highly topical issues in the philosophy of biology. Overall, the project will demonstrate that, despite all efforts to consign it to the dustbin of history, organicism has never been more relevant than it is today. The main output of the project will be an extended monograph, already under contract with MIT Press, which will eventually appear as part of the Vienna Series in Theoretical Biology.