As confirmation of his hypothesis that individual identity is an illusion, Mogensen first turns to the kind of language used in relation to individual identity. If this language shows a strong correlation with the essentialist language, this provides, if not proof, at least a strong suggestion that psychological essentialism is at play in the former.
The author is quick to establish the first of several such correspondences:
The belief that certain traits are more central to who we are and others more peripheral seems on its face to straightforwardly embody the key essentialist assumption that although individuals have various recognisable surface qualities they also have certain core properties which properly define them (p. 27).
Again, the idea that core properties are more determinative of a thing than surface qualities maps rather straightforwardly onto the version of psychological essentialism here under consideration.
From this more general point, Mogensen makes clever use of the candidate principles which he has heretofore treated. For, in each of them, he finds the doubling of a key feature of essentialist thinking:
[A] number of philosophers suppose that our core traits are typified by their durability. Similarly, a key feature of essentialist thinking is the assumption that essences are durable and likely to persist throughout observable changes. Many philosophers have supposed that our central traits exhibit depth and breadth of influence. In the same way, it’s assumed that essences typically cause the observable properties of individuals and exhibit high inductive potential. The behavioural penetrance that we normally associate with our central traits can in principle break down, as in cases of inauthenticity. Similarly, in spite of their characteristic inductive potential, essences can in principle be masked by surface qualities, as in the example of a horse modified to behave and look exactly like a zebra (p. 28).
As go durability and depth and breadth of influence, so goes psychological essentialism.
While it would prove easy enough to concede the points above, it is worthwhile to ask what becomes of the candidate principles of uniqueness and reflexive attitudes. We might wonder whether they also mirror central aspects of psychological essentialism. Although uniqueness seems to map onto essence rather straightforwardly (by way of example, we need only allude to Leibniz’s treatment of essence, substance and monad), it remains unclear to what extent reflexive attitudes can be integrated into a reductive account of individual identity to essentialist thinking, i.e. whether it be a hallmark of being an essence to reflect on one’s essence.
Yet the author finds the most damning evidence of essentialist thinking with regards to identity in the fact that no philosopher has yet proposed a plausible general account of trait centrality in individual identity. Just as his point-by-point refutation has shown, each candidate principle issues in incoherence when put to the test. If we persist in maintaining existence claims about individual identity despite the lack of plausible candidate principles, this must arise from an innate disposition which resists both external and self-correction:
Lastly, the fact that we believe so confidently in the reality of individual identity in spite of lacking any plausible account of what identity centrality consists in may be thought to reflect the essentialist disposition to automatically project essences without any clear understanding of what those essences might be (p. 28).
In these points, Mogensen finds considerable evidence suggesting that individual identity (in the narrow sense being treated here) does not exist as a subsistent or metaphysical entity. If the question remains whether it may possess reality of another sort (e.g. effective or practical reality for the subject), it seems clear that we shall find no persistent object to which individual identity as such could pertain and this by lack of real principles determining identity centrality.
The author is not, however, content to rest on the conclusions which the reader might otherwise draw from the case which the former has made to that point. He evokes several empirical studies to cement the issue. In the study, a team developed:
[…] an essentialism index designed to capture the extent to which different personality traits are associated with assumptions characteristic of essentialist thinking (inductive potential, durability, etc.). In comparing a trait’s score on this index against judgments of identity centrality made by undergraduate psychology students, they found that most of the variation in centrality judgments could be predicted by differences in the extent to which personality traits are essentialized (p. 28).
Certainly, empirical results inevitably require a certain level of interpretation. Such findings can always be turned on their head in that correlation neither predicates causality nor explains the direction of presumed causality. Mogensen himself notes:
This finding is merely correlational, leaving open the possibility that essentialist beliefs are explained by judgments of identity centrality, rather than vice versa. However, given the status of psychological essentialism as a pervasive and deep-rooted mental disposition, the converse is surely the more plausible causal hypothesis (p. 28).
If approaches to individual identity prove unsound on both the conceptual and the empirical level, it seems difficult to make much of a case for keeping them. Still, the question must be asked whether there remains room for maneuver with essentialist thinking or whether the complex is wholly beyond saving.