“I cannot pretend to agree with him, when I know that his mind is working together under a delusion — Trollope (1869)
Very rarely does anyone claim to be deluded. Anthony Trollope, in his novel He Knew He Was Right, describes not only the totally destructive effect of delusional jealousy on the individual himself but also the extraordinary dilemma this poses for other people who come into contact with him: whether to humor the individual and risk reinforcement or to confront him and risk violence.
A delusion is a false, unshakeable idea or belief that is out of keeping with the patient’s educational, cultural and social background; it is held with extraordinary conviction and subjective certainty. Subjectively, or phenomenologically, it is indistinguishable from a true belief.
Characteristics of Delusions
It is important to understand the following characteristics of delusional thinking:
To the patient, there is no difference between a delusional belief and a true belief — they are the same experience. Therefore, only an external observer can diagnose a delusion. A delusion is to ideation what an hallucination Opens in new window is to perception.
The delusion is false because of faulty reasoning. A man who is a Bachelor of Medicine of the University of London holds a delusion that he is being used as ‘an envoy from Mars’. He believes that he is both a doctor and an envoy, and neither thought seems to him to be delusional or imaginary. He likes to imagine himself a rich man with an estate in Gloucestershire. He has not the slightest difficulty in identifying this latter idea as fantasy.
To the man himself, a delusion is much closer to a true belief than imagination, and the reasons enlisted to support its veracity are produced in the same way that a person would prove any other notion on which he was challenged.
Normally, fantasy is easily distinguished from reality, although the subject may show great reluctance in accepting his aspirations as ‘mere fantasy’. Similarly, there is usually very little difficulty for the external observer in deciding whether a false belief is a misinterpretation of the facts based on false reasoning, or a delusion.
It is out of keeping with the patient’s social and cultural background. It is crucial to establish that the belief is not one likely to be held by that person’s subcultural group, e.g. a belief in the imminent second coming of Christ may be appropriate for a member of a religious group, but not for a formerly atheist, middle-aged businessman.
Primary delusions are not understandable and are psychologically irreducible, while secondary delusions are understandable in the context of preceding affects or other experiences.
The emphasis in primary delusions is on the form of the symptom, i.e. how they originate, rather than the content.
Jaspers termed primary delusions as delusions proper and secondary delusions as delusion-like ideas. He suggested four types of primary delusions:
delusional atmosphere,
delusional perception,
delusional ideas and
delusional awareness.
Similarly, Schneider (1959) divided delusions into delusional perception and delusional notion. He described delusional perception as a two-stage process, in which abnormal self-referential significance is attached to a genuine perception without any comprehensible rational or emotional justification (i.e. it is not understandable). Perception itself is not altered but the meaning attached to what is perceived is altered.
Delusional perception may arise out of delusional mood (also known as delusional atmosphere). Delusional mood is akin to a pre-delusional state or ‘precursor phenomena’, during which the person has a vague feeling that something odd is going on.
Delusions arising out of delusional mood are considered primary delusions because they are vague, their content does not refer to the delusional mood and they are not understandable.
The notion of a primary delusion arising from a preceding primary delusion (delusional mood) is confusing but as Sims (1995) points out,
the core of a primary delusion is that it is not understandable (and contain not any temporal relationship).
Sudden delusional ideas are also classified as primary delusions (Fish 1967).
Secondary delusions are easier to understand as they arise from other affects, such as depression, and from phenomena, such as hallucinations. Thus, secondary delusions are always interpretations, and are psychologically reducible, for example grandiose delusions in mania or persecutory delusions secondary to hallucinations.
