This article is concerned with two interrelated questions: what, if anything, distinguishes synthetic from natural organisms, and to what extent, if any, creating the former is of moral significance. These are ontological and ethical questions, respectively. As the title indicates, I address both from a broadly neo-Aristotelian perspective, i.e. a teleological philosophy of life and virtue ethics. For brevity's sake, I shall not argue for either philosophical position at length, but instead hope to demonstrate their legitimacy through their explanatory power. I firstly argue that synthetic organisms differ in kind from natural organisms and machines, and differ only by degree from genetically modified organisms. I then suggest that this is nevertheless sufficient to give us specific ethical reservations about synthetic biology: namely, that more than any other widely used biotechnology, it is characterised by a drive to mastery that stands opposed to due appreciation of the giftedness of life. Keywords Synthetic biology. Virtue ethics. Aristotle. Teleology. Philosophy of technology. Hans Jonas The Bifurcation of Nature Synthetic biologists seek, broadly speaking, to create novel organisms using standardised biological parts and in accordance with engineering principles. The present analysis of synthetic biology will begin with the ontological question of what kind of beings synthetic organisms are, arriving at an answer by drawing comparisons with machines, natural organisms (henceforth 'organisms'), and genetically modified organisms (GMOs). First of all, therefore, we must define these entities, so as to clearly distinguish between them. To some this might seem unnecessary. In fact it is anything but: not only do biologists and philosophers of science frequently describe organisms in mechanistic terms for heuristic purposes (which we might excuse), but many also go further and suggest that organisms actually are a kind of machine [1]. This ontological claim is, I believe, wholly erroneous and serves to undermine ethical analysis concerning both human and non-human life. This misconception has a long and distinguished philosophical pedigree, however, stretching back at least as far as Descartes. Dividing the cosmos into res extensa and res cogitans, or 'extended' and 'intelligent' substances [2], Descartes' ontology promoted a theoretical 'bifurcation of nature' [3]. 1 The former substance, res