In “Is individual identity an illusion?”, Mogensen examines at some length four candidate principles for explaining identity centrality: durability, uniqueness, depth or breadth of influence, and reflexive attitudes. While Mogensen is doubtful on the viability of any one candidate principle, he does leave open the possibility of their concurrence or multiple instantiation as a means of explaining identity centrality:
I don’t presume that there is a single determinative property whose possession is both necessary and sufficient. There may be a number of different properties whose instantiation counts to some extent toward the centrality of a trait (p. 8).
Leaving aside whether such an endeavor to isolate a priori candidate principles is itself misleading, we will now spend some time with the treatment given to each of the principles above.
Mogensen opens his reflections on 1.) durability with an illustration:
Imagine Jane, a person in a constant state of flux. Her tastes bounce back and forth between various extremes. Her religious beliefs shift quickly from Anglicanism to Hinduism to Mexicayotl. Even her character is fluid from one week to the next. It may seem natural to say that Jane has no identity. Unless there is some enduring aspect of herself that she keeps hidden, she has no true self to speak of (p. 9).
The author judges that an example of this kind leaves the reader with the impression that a trait’s durability goes a long way in determining its centrality to identity. Our intuitions, as well as considerable secondary literature, likewise lend themselves to such an interpretation. Yet durability, as presented above, hides a certain ambiguity insofar as a trait’s duration to that point says little about its durability or capacity to resist change. For:
Durability is a dispositional quality. Roughly speaking, it is the disposition to resist change in the face of certain stressors. A trait of low durability might be held for considerable time if never challenged. A highly durable trait might vanish straightaway if subjected to extraordinary force. For this reason, it seems implausible that de facto duration matters to identity: the actual persistence of a trait depends as much on extraneous forces as it does on the nature of the trait and its bearer.
Mogensen seems right to make this point. Barring a test for the trait’s resistance to internal or external pressures, there can be no way of knowing whether its duration to that point owes to its own make-up or to happy circumstances. By way of example, a porcelain vase might exhibit great duration if handled properly without ever being recognized as a durable entity.
This may read like a case for required testing for durability, but, as the author notes, it is unclear what form this testing might take. He elaborates:
With respect to judgment-sensitive attitudes like beliefs and desires, it seems natural to suppose that their durability is a function of their capacity to resist revision in the face of reflection and deliberation (p. 10).
Yet not all traits considered important to identity fall under the heading of judgement sensitive attitudes. We need only consider one’s ethnicity, language, sexuality or nationality as traits at which the person does not arrive by means of reflection and deliberation; therefore, these cannot sensitive to judgment in the same manner as beliefs and desires which represent important identity traits.
Certainly, we might contend that beliefs about the former properties (e.g. “my language is x”, “my sexuality is y”, etc.) could fall under procedures of this sort and prove the sort of thing about which a person might prove mistaken in special circumstances. But the properties themselves remain otherwise insensitive thereto.
Mogensen then turns to the question of just which such beliefs resist such revision and finds the answer at odds with our expectations concerning identity. He writes:
[W]e should note that many of our most firmly held beliefs seem completely peripheral. Examples include my belief that that water is wet and that 2 + 2 = 4. My moral and religious beliefs are a good deal shakier, but would be said to be far more central to who I am (p. 11).
Since trivial propositions can be the subject of judgment-sensitive beliefs and trivial propositions preclude revision in virtue of their form, on a version holding up centrality as durability as resistance to revision, trivial propositions would figure among the most central of our identity traits. In contrast, the heavily evaluative propositions which organize thought, speech and deed prove more tentative and necessarily subject to revision over time, given the best account of things then available. So, by this standard, those propositions which seem most to structure identity would be furthest removed from the criterion securing their structuring role.
On the point of durability, Mogensen proves persuasive, marshalling a number of arguments against this particular candidate principle. Yet some may find that the author has stacked the deck against the criterion from the outset by including trivial propositions in the set of judgment-sensitive beliefs the resistance of which is to be tested. For such beliefs are likely to prove just those which are insensitive to judgment of the relevant kind by dint of their form.
Additionally, it might be contended that identity-constituting beliefs are most likely to be evaluative or normative in kind whereas those beliefs presented here are factual or descriptive. The latter would hence follow from a verification to which the former cannot be made to fit. Were the class of candidate beliefs restricted to evaluative or normative, as Taylor would have us believe of identity-constituting beliefs (Sources of the Self, pp. 29-30), the result could prove rather different. But the author might see in this little more than an ad hoc attempt to save an obsolete category.