The anti-essentialism motivating the posthumanist turn tacitly rejects realism about two distinct forms of essence: descriptive and prescriptive. The first relates to the absence of any objective correctness or naturalness as to the boundaries of the concepts we apply in language and thought, let alone the essence concepts (sortals) that denote the primary kind to which a thing belongs and to which it must belong in order to continue existing. The second rejected form of essence is something intrinsic to things that objectively grounds ways in which it ought to function, develop or be fully actualised. For example, there is nothing inherent to some intrinsic human nature that determines the conditions of best being a human, i.e. our form of the good or our telos.
That second aspect prompts a question about what to do with naturalness talk. We tend to talk about natural and unnatural ways for things to be and behave, whether we are discussing people, animals or physical systems. This is not to be confused with the related dichotomies between the natural and the artificial, or inherent disposition as opposed to extrinsically induced behaviour. Those dichotomies might be relevant to a descriptive essence. Instead, the relevant naturalness appears to relate to the duality in all things between the way that it manifests at any given time and an actual or potential ideal form somehow encoded within it, or more specifically, its capacity to function properly or to malfunction.
The anti-essentialist cannot abide this essentialist explanation of naturalness talk, and there are strategies for dealing with it. One such strategy is to eliminate this kind of talk on the basis that it is a wrong-headed folk theory about the world that has been found wanting due to the superior explanatory power of purely causal theories of biology and physics. The problem with this approach is that it risks leaving out aspects of reality that it finds difficult to explain, yet of which we have strong intuitions.
A second strategy is to retain naturalness talk, but on the basis that it really maps onto socially constructed kinds rather than truly intrinsic essences. On this view, socially reinforced attitudes harboured as though there were such essences, by a critical mass of community members, make it true in a well-founded fiction, or otherwise true relative to the capacities and practices of that community, that they do have such essences. These essences, being socially constructed, can vary between communities, and shift with the changing norms and mores of the community, but the naturalness talk associated with these essential ways of being is still validated within the social life of the community.
This does provide a way to justify continuing the naturalness talk, but it does not do justice to the respect in which naturalness talk aims beyond culture towards standards by which cultures can be judged. Thus, the social construction strategy actually turns out to be the elimination strategy, because we must change the functional meaning of naturalness talk in order to keep it, and this would amount to not keeping it at all by the standards of those actually committed to naturalness talk.
A third strategy, and my preferred approach, is to separate out the ideal form of things supposed to inhere in their prescriptive essence. The ideal is not to be regarded as intrinsic to the being of any given thing or its kind. Instead, it is an extrinsic normative demand on things quite apart from (but overlapping with) extrinsic normative demands on moral and rational agents. Just as agents (persons) must act in certain ways to meet the requirements of morality, and order their mental states in certain ways to meet the requirements of reason, all organisms and systems must function in certain ways in order to meet the requirements of naturalness for a given kind. The consistent theme, here, is the extrinsic imposition of all normative demands.
This is an anti-essentialism precisely because it locates all normative demands with an extrinsic source, rather than in some universally invariant feature of the thing itself or of a kind to which it belongs. Despite retaining the theoretical potential for universal normative demands, this is a significant departure from the view that to behave naturally is to realise something intrinsic to something of a given kind, because it comports with the rejection of descriptive essences described at the beginning of this post. It means that the criteria for belonging to a specific kind – and especially what it means to be human – can have unprincipled and historically contingent boundaries, as is actually suggested by our best contemporary theories of biology, and yet be the subject of universal norms of morality, rationality and naturalness imposed extrinsically on that messy and contested kind.
Where both the descriptive and prescriptive forms of extrinsic imposition find their source is a separate question. It suffices, in principle, for an anti-essentialist to note that it need not be intrinsic to things of the kind or to the kind regarded as a universal. Even so, given that this is a blog about theistic posthumanism, and thus theistic anti-essentialism, it should be anticipated that the source will ultimately be identified with the divine will.
If this is the right way to vindicate naturalness talk, then it follows that it is not possible to derive a viable ethical theory from our intuitions of what is natural and conducive to flourishing for kinds such as humanity, because such conditions will depend on a normative demand of naturalness that derives from an extrinsic and possibly transcendent source. Whatever that source is will presumably provide a more direct grounding for moral truth claims, rather than needing to derive them indirectly from related but distinct intuitions of naturalness.
Theocentric Posthumanism 