The species of vitalism discussed here is a malleable construct, often with a poisonous reputation (but one which I want to rehabilitate), hovering in between the realms of the philosophy of biology, the history of medicine, and the scientific background of the Radical Enlightenment (case in point, the influence of vitalist medicine on Diderot). This is a more vital vitalism, or at least a more ‘biologistic,’ ‘embodied,’ medicalized vitalism. I distinguish between what I would call ‘substantival’ and ‘functional’ forms of vitalism, as applied to the eighteenth century. Substantival vitalism presupposes the existence of something like a (substantive) vital force which either plays a causal role in the natural world as studied by scientific means, or remains a kind of hovering, extra-causal entity. Functional vitalism tends to operate “post facto,” from the existence of living bodies to the desire to find explanatory models that will do justice to their uniquely ‘vital’ properties in a way that fully mechanistic models (such as Cartesian mechanism) cannot. I discuss some representative figures of the Montpellier school as being functional rather than substantival vitalists, particularly as regards the models of organic organization which they develop, and make some suggestions as to how these relate to the then-nascent science of biology.