Today I'm going to outline a template for understanding psychosis using dynamic systems theory. It is not itself a theory, being far too rudimentary. But it is perhaps a scaffold on which a theory could be built.
Here are some central ideas from dynamic systems theory. First, a dynamic system is one that keeps itself in balance. It self-regulates - like our home heating systems with their thermostats linked directly to the boilers to turn them on and off. Second, it does this in response to the demands put on it by the local environment. In hot weather the body sweats more to cool down; when it cools down enough, it stops sweating. The internal milieu is thereby maintained. Third, complex systems are autopoetic: the systems are self-creating, not simply maintaining a pre-existing structure within certain homeostatic limits, but rather organising and repairing their own structure. Fourth, such systems can operate at different levels of equilibrium. We do not have to do with a single mode of functioning that is maintained despite the pressures it is under. Rather we have to do with a system that, when maintaining its equilibrium in one configuration becomes highly challenged and too difficult, can jump to different forms of organisation that cope better with the particular challenges now encountered. Quite different orders emerge out of the same ingredients through saltatory steps.
And here is the application to psychosis. First, that everyday perception and cognition which is amenable to 'reality testing' involves one mode of organisation, which is maximally adaptive to the demands of the situation. At its best this mode promotes maximal engagement and maximal self- and other-understanding. However it leaves one vulnerable to hurt, rejection and to needs not being met. Second, that psychosis involves a step into a quite different mode of organisation, a mode which shortcuts reality testing. At this simpler level of functioning, fantasy and reality collapse into one another. Wish and fear are not now separate from real experience: the system is no longer expending energy to keep the two functions of fantasy and reality separate. Third, that the system moves into this mode of functioning when the emotional stressors on it are, for the domain in question (reality testing is not a global cognitive faculty; it operates in many different domains, and a person only becomes out of touch with reality in a limited range of these domains: patients are not usually globally psychotic), too great to handle. Fourth, that anxiety is a perturbation, an instability, in the dynamics of the system - a perturbation enough to invite a transition from a normal into a paranoid mode.
Fifth, It takes energy to separate reality from fantasy. Making the self-other distinction takes effort. Drawing the line between you and I in the right place involves a relaxed flexibility. Tiredness and overwhelm get in the way. We are normally sustained in our reality-contact by healthy relationships and by 'internalisations' of healthy relationships. By the latter is meant: we have developed forms of complex stability-promoting reality-contact through early relationships, and these sediment out a reliable re-usable structure within the self, a capacity to now enter adaptably into new relationships and maintain the stable but flexible give-and-take that constitutes real relating.
So, the main point of the dynamic systems framework for thinking about psychosis is the way it helps us think about the relation between psychotic and non-psychotic modes of function. One of the clinician's therapeutic tasks is to help a local system to change its total form, to find the small nudges that will enable a quite different order of world-relation to emerge. The framework also helps us to not focus on the content of delusional beliefs (although such content may provide important clues) but instead to think about the embedding system and its mode of function. Given that the different systems (psychotic and non-psychotic) are enactive in character, involving different perceptuo-motor cycles for example, the stabilisation of a transition into a non-psychotic world could be aided by particular forms of self-world engagement.
Another way in which the dynamic systems framework is, I hope, relevant is that it is not intended as a metaphor for a psychological theory. The difficulty I am imagining, for the system which is finding itself unable to continue to self-organise in a reality-contact-oriented manner, and which therefore makes a saltation to a psychotic mode of function. The details of the delusional world are the result of such a saltation. The very form of mind consequent on the saltation is quite different. It is not that we have to do with psychological steps - rational, emotional, or otherwise psychologically intelligible steps - within a mode of function.
I say: not a psychological theory - but of course what does and doesn't count as psychological is not a hard and fast fixed concern. One theory which we might want to call 'psychological', and which I believe is compatible with the outline I'm offering here, is Bion's idea of a breakdown in what he calls 'alpha function' in psychosis. The idea is that it is the processes which lead to the genesis of normal mindedness which itself becomes unbearable and unfeasible in psychosis - i.e. that it is not processes which occur within already formed minds which are in trouble.
To take just one possible example, imagine if a personality, rather than being able to body forth into a psychologically unified single sexual identity, tried to do justice to its own proto-sexual libidinal drives by sedimenting now or then in two different gendered directions, neither of which had space within it for the articulated mind-creating forms of the routes of instinctual satisfaction of the other. An unstable oscillation could result if normal repressive mechanisms did not suffice to cut off the identity which another dominant identity could not accommodate. The mind would be torn apart, and psychosis would result when conflict at a purely psychological level became unmanageable. The result is a shift to a different level of neurological self-organisation in which the very project of reality-contact - i.e. the project of allowing desire and perception to organise a stable self-world distinction and interaction - would in this domain be abandoned.
The psychotherapeutic task would here be one of trying to create a broader identity to accommodate all of these instinctual consolidations - and I think it important to note that this task is not best understood as one of merely developing a bisexual self-conception, but rather one of the lived body itself somehow developing a hitherto missing libidinal flexibility.