One is Borderline Personality Disorder. Why it fires the imagination of the mental health professionals is too complex an issue to take up here in any detail. Suffice it to say the main reason lies in the fact that the concept has no true existence at all. It is the failure to identify the actual problems of the patient, out of one's ignorance of how mental issues should be analyzed and understood, which has caused the profession to artificially create the concept of Borderline Personality Disorder. And since humans love to wage the most passionate polemics on trivialities, it should not surprise us that the concept of Borderline Personality Disorder invites a limitless scope to get profound.
And boy do they get profound on this topic. Every lecture that I have attended on Borderline Personality Disorder starting from the great Otto Kernberg himself, to his wife - isn't it strange that both husband and wife are experts on the same illness - to other lesser specialists, I have invariably found it to be so erudite that after the first five minutes every member of the audience appears to be grasping for straws if not outright baffled as to what is going on. And therein lies the second reason for its appeal. If nobody can make out head or tail of what the speaker is talking about then each member of the audience can feel equal to everybody else - obfuscation is a great leveler. The last, and for that reason not any less important, reason is the belief, or rather a fear, which an astonishing number of mental health professionals are plagued with, that they themselves have a touch of Borderline Personality Disorder. In other words the irrational aspect of themselves which they don't understand they think it must be the borderline behavior present in them.
And what lies behind the irrational, erratic, and very cleverly annoying behaviors of the so called Borderline patients that mental health professionals cannot scream enough as "splitting" - a concept that was introduced by Freud and never with any intention for it to be used as an pejorative epithet against the patients- which gets their goat? It is a negative transference towards authorities stemming from their rage at their parents for not doing enough for them. Making staff members on the hospital ward fight with each other - the so called splitting - is at bottom nothing but making the parents fight with each other. And their self-destructiveness is also often a way to punish themselves but at the same time a means to annoy and frustrate authorities (parents).
The lure of Lucid Dreaming is little hard to figure out. But there is no doubt that any lecture on the topic will cause the folks to jam pack the lecture room to the point of overflowing into the corridor. And the psychology of its appeal appears to lie in the hope of finding some great pearl of wisdom there which will enable one to start dreaming lucidly oneself. And behind this desire lies another desire: the hope of curing ones problems by lucidly dreaming and directing them to resolution. It is therefore driven by a desire for self-therapy. And this brings me to the unpleasant task of bursting the bubble of enthusiasm surrounding lucid dreaming. There is not much to its metapsychology. Lucid dreamers are people who are more awake while dreaming than others.
Dreaming is a state of semi-wakefulness to begin with - the failure of our ego to go to sleep completely (complete withdrawal of cathexis) - and not some special third state of consciousness which neither belongs to wakefulness nor sleep as that completely idiotic Activation-Synthesis hypothesis used to claim. While dreaming we are only partially sleeping. Part of our brain gets activated and awake. This is why, if one fully wakes up a person out of intense dreaming, he can quickly get oriented to the real world. The neuronal networks responsible for wakefulness are already partially in gear.
Now individuals differ greatly in the ratio of their wakefulness and sleepiness while dreaming. Some tolerate high degree of partial wakefulness while dreaming, others do not, and get out of dreams/sleep altogether at quite low thresholds. Lucid dreamers appear to be individuals who can continue to dream while the centers responsible for wakefulness are quite active. They are individuals who can more easily ride the two horses of partial wakefulness and dreaming at the same time. They can divide their consciousness into taking cognizance of the dream world and the real one at the same time.
The psychological mechanism behind this appears to be similar to how hysterics can tolerate co-existence of multiple personalities. People who are highly suggestible and enter into hypnosis easily - traits of hysterical disposition - appear to have greater ability to dream lucidly. While dreaming their mind splits into two states of consciousness, one aligned to the real world and the other to the dream world. The first state can even influence the course of what is happening in the second state. And this is felt by them to be a special gift akin to some magical ability. It is the wish to acquire this magical ability which underlies the fascination with this phenomena. The lure of Lucid Dreaming is at bottom a lure of magic and a desire to become a magician with one's dreams and one's problems.