I'm not here concerned to resurrect the concept of primary delusion, but am instead concerned to tease apart matters epistemological and psychological which matters often get run together in the psychological literature and which in the process make for the appearance of psychology rescuing the patient in her intelligibility from the inattention of psychiatry. In the last paragraph, for example, I talked blithely of 'normal processes of sense-making' as if we all already knew perfectly well what is meant by talking in that way - as if it were straightforward to assume that 'reasoning' and 'inference-making' and 'understanding', for example, are helpfully understood as names of mental processes. As if we can know whether or not understanding is to be met with, for example, by considering whether a certain information-transmuting temporally-extended mental event or sequence of such events is here going on. The slip from talk of understanding as personal ability or capacity or epistemic achievement to talk of understanding as mental process may look innocuous, but what I'm developing here is the idea that it obscures the fundamental matter at stake for Jaspers, in treating of delusion, which is whether or not we, anyone, can really find his comprehending, empathic, sense-grasping feet with the psychotic subject when he is in his delusion, or whether delusion as such repels comprehension.
Let's first remind ourselves that, despite the calumnies of contemporary psychologists, Jaspers is happy to concede that there are senses of 'understand' - perhaps those closer to 'explain' for those who like to keep their understanding and their explanation in separate conceptual categories - which are appropriately deployed in talk of a true understanding of true delusion. We may for example understand the causal genesis of a delusion in terms of the motivational work it does for the delusional subject. We may understand perfectly well why someone could be motivated - in terms of not simply boosting their morale or self-esteem, but in terms of making life bearable at all - to maintain that they are the Archduke Ferdinand. And drawing on psychodynamic forms of explanation we may turn this question of motive into an answer not about intention but about causation: the delusion was formed and sustained because of the way it makes life more bearable. This can be true not only of grandiose but also of paranoid delusions: it's more bearable to believe that the Vatican has it in for you because of their hatred of what you think they allege are your sexual desires than it is to experience the dissolution of your mind under the aegis of an as-yet-un-split-off,-as-yet-un-projected ego-destructive superego and as-yet-un-integrated sexual desires. Jaspers was no big fan of psychoanalysis, but even he was happy to go along with such causal-motivational understandings of various bona fide delusions. (Jaspers: ... ‘understandable connections do [indeed] play a part … in psychoses so far as content is concerned’. .... We ‘may well understand from the context how a delusional belief liberates an individual from something unbearable, seems to deliver him from reality and lends a peculiar satisfaction which may well be the ground [would motive be a better translation?] for why it is so tenaciously held.’)
The sense of 'understand' we are after, however, has as I said not to do with psychology but with epistemology. We may understand why someone is motivated to believe that they are the Archduke Ferdinand, yet still not at all be able to take being Archduke Ferdinand as an intelligible, thinkable, thought. How can someone who knows where he was born and who is parents are and what year it is and so on yet believe that? Isn't that the kind of thing you'd 'have to be mad to believe?' Laing asks somewhere who is the madder person: the girl who thinks that there's a nuclear bomb inside her stomach, or a prime minister who's got his finger on the nuclear button? The answer, I think, is the former: the sense in which Hiroshima was unthinkable is rather different from the sense in which taking something large to be fitted inside something small is unthinkable.
Let's even concede that when a sane and grounded person is arriving at her beliefs and when a delusional person is arriving at her delusions they may both have something like the same processes going on inside their heads. They both have one thought after another, all the thoughts associatively give rise to further thoughts, and so on. Let's imagine, what is surely often-enough true, that the delusional person is even more busy than normal trying to 'make sense of' what's going on, and that if you asked him carefully he might offer his delusions as explanations for certain rather strange experiences he has. What none of this shows, though, is that he really does make sense of the strange experiences, rather than arriving at those illusions of sense we call 'delusions'. For... if one's feet aren't on the ground then it doesn't matter what goes on in your head: crank the normal associative mechanisms as hard and rigorously as you like, and you still won't get a sane output. Sure, delusional thinking may often be a valiant attempt to make sense of crazy experiences. Sure, the inferences involved in the delusional thought may be no less logical than the motley that make up the reasoning of the sane subject. Still, if you start from there then, try as hard as you might, you'll never get to somewhere called 'reason'.
In his 1812 Philosophical Essay on Probabilities Laplace offered that “the more extraordinary the event, the greater the need of its being supported by strong proofs”. What in one context may count as a reasonable degree of evidence provision or a reasonable degree of care in reasoning will not count as such in another context. It's not the maxim - which perhaps doesn't apply here - but rather the moral - that reasonableness is not guaranteed by mere quotient of reasoning - to which I'm here drawing attention.