This article examines the use of technics and polemics within contemporary animal rights discourse. It focuses on the Nonhuman Rights Project, a group which is currently engaged in litigation in the United States aimed at having a non-human animal recognized by the courts as a person and subject of rights. Turning to the work of the late legal historian Yan Thomas, this article explores the degree to which the categories of person and thing have tended to become sacralized in the modern discourse of animal rights in order to refashion them at a polemical and metaphysical level. This is then contrasted with the work of Roman jurisprudence which, in Thomas’s account, was capable on the contrary of filing its metaphysical categories back within the narrow technical world of the civil law. The history of legal categories reveals in this sense some of the tensions which today beset the discourse of rights in relation to the non-human.