Just a note, a sketch of an argument, not yet referenced, not yet tested on the source material...
There's a rather too breezy picture of our inner life that sometimes gets going in the mentalisation-based psychotherapy literature. The idea we are offered is that the person 'with', say, 'borderline personality disorder' sometimes - when under emotional strain - struggles to 'mentalise' - to think folk-psychologically about their own and others' experience and understanding. So they are left with 'un-mentalised' experiences - this literature's way of spelling out what inadequate 'alpha function' (to borrow Bion's more helpfully vague formulation) might amount to - that at worst get rendered in a merely somatic idiom (self harming then being called on) or get framed by the sufferer in what is, psychologically speaking, a too simplistic manner (e.g. teleologically in relation to her own experience rather than properly intentionally in relation to the distinct projects of others - by which is meant: if I am hurt by what he did then what he was aiming at was hurting me etc.). The idea of the disorder's apt therapy is then said to be to encourage mentalising in the midst of, or at least before and after, that emotional turmoil which tends to derail it and send the patient off into situations of chronically dysregulated affect.
I said this is rather too breezy because, it seems to me, it risks portraying the work of therapy in such instances in far too simply cognitive a spirit, as if the patient is mainly struggling in their thinking when under emotional strain. That they are. But, it seems to me, the more significant aspect of the problem the patient faces at such times is not one of not recognising qua understanding what and why they or some other are/is thinking or feeling or doing what they are thus thinking or feeling or doing, but one of not, as one might put it instead, offering themselves or others apt recognition in their inner life. This ethical-existential disturbance is, it seems to me, what really drives the disruption to cognition we meet with in such moments of psychological crisis. However it can be hard to see that this is the case because we tend to think of ethical-existential matters as secondary to the real psychological action - as an overlay on top of human nature, as it were, rather than its fons et origo. Here, however, I suggest that the ethical achievement of bearing oneself and others in mind, of showing/achieving personal understanding rather than merely correctly grasping his or her meaning, is the primary mind-forging crucible on which meaningful thought about self and other depends.
In fact I think we know this perfectly well when we're in the midst both of really engaged clinical practice and when we're going about that daily business of tending to our relationships with one another. Why is it I find it hard to think clearly or understand myself in the midst of this encounter with my sometimes difficult friend or my often intrusive sibling? Clearly it has to do with what difficulty and intrusion really amount to. They amount to a disturbance in the ethical axis traversing the heart of the self which axis is presupposed by any realistic cognitive endeavour. What is too much or too little by way of involvement, helpfully leaving one another alone, being there for one another, offering firm support, showing and taking care but not tiptoeing around, calling someone on their shit, honouring their distinctive values, giving them their and receiving our due, trusting them and receiving apt trust from them, not letting ourselves be taken for granted or exploited, being shown and showing consideration, being true to oneself, essential openness or gullibility, being held in mind enough, loved enough, expecting too much or too little?
This terrain has famously been best charted by psychoanalysis, with its focus on such self-other relations as make for stable or fractious self-identity and other-relations. The oedipal triangle is perhaps the best known such situation: I want my mother to myself but someone else, some much older fellow, keeps taking her mind away, and its too much. Or perhaps it's my older siblings taking her away. And I like to play with them and I also hate them, and can I trust them, and are they helping me or undermining me with their advice, and am I really cared for by my friends because of who I am or because of my more extrinsic social or physical attributes? This unstable terrain is that of the passions and of our greatest sensitivities. It is what is maximally evoked in the transference, which is why it is hard to imagine a real therapeutic cure which does not work at the depths that pretty much only the transference sounds out. It is what much of our pseudo-mature adult lives does its best to cover over, avoid, neglect, disguise. It is the zone of maximal latent fractiousness at the core of the self. Our self, our value as people, our spontaneous capacity for and unearned desert of goodness: such are what is on the line in those moments of mind-dementing argument which also, as it happens, results in the greatest disturbances in the apt ascription of propositional attitudes known as mentalisation.