Delusions: Examples, Definitions, and Theories.

What Are Delusions?

There are general and specific ways of understanding delusions. Herein, we shall cover a general understanding of delusions before dealing with more detailed and particular accounts of delusions.  So, generally speaking, what is a delusion?

A delusion is an idiosyncratic belief or impression that is firmly maintained despite being contradicted by what is generally accepted as reality or rational argument, typically a symptom of mental disorder.

This definition of delusions says two important things. On the one hand, it asserts some version of the correspondence theory of truth; which is the view that truth is always in relation to or correspondence to some objective and mind-independent reality: an extended and factual condition. It asserts the correspondence theory of truth by claiming that delusions arise from a failure to accept what reality really is; only because such presupposes a common feature in the world which can be intersubjectively perceived in some correct or true fashion.

On the other hand, it asserts that delusions are identified, in part, by their deviance from common beliefs – what is generally accepted as reality or rational argument.

As simple and straightforward as these two assertions are, they are controversial. For example, the correspondence theory of truth is rooted within unjustified assumptions – (see the munchausen trilemma to understand how) – and some beliefs which are wide-spread can indeed be false: i.e., that the earth is flat, or that taxation is theft.

In addition, delusions seem to be more than what the previously given definition states; for instance, the Stanford Encyclopedia of philosophy believes instances of delusions are:

  1. Delusions are seldom relinquished in the face of evidence; those who are of a delusional belief do not respond to evidence.
  2. Delusional beliefs are reported with sincerity and conviction. Although, the degree to which a person adheres to the delusion can vary.
  3. The behaviour of the person does not always match the content of the delusional belief.
  4. The delusion is often a source of distress and can impair daily functioning: e.g., paranoid delusions or delusions of persecution can result in the victim of the delusion distancing themselves from friends, families, and co-workers.

So, clearly the simple answer to “what is a delusion?” fails to provide a satisfactory account of delusions. So what are the more detailed accounts? Lets start by clarifying some basic confusions about what delusions are and giving two examples of clinical delusions.

Examples Of Delusions

Two examples of common delusions are Cotard delusions and Capgras delusions. Cotard delusions are part of a larger syndrome involving other symptoms such as anxiousness and depression. Patients who suffer from these delusions believe they are dead or no longer exist.

A Capgras delusion refers to the delusional belief that a person’s friend, family member, or pet has been replaced by an imposter. The delusion revolves around the misidentification of people or objects.

The Difference Between Delusion And Hallucination

When we speak about delusions, we are in reference to something quite distinct from a hallucination. However, there are, unfortunately, as equally many conceptual issues with defining hallucinations as there are with defining delusions, so we shall rely on a handful of definitions to characterize hallucinations, since we shall refrain from any rigorous account of hallucinations.

Definitions Of Hallucinations

  • Hallucination is a false perception characterized by externalization and a continued belief that the experience is a perception of something outside the self rather than internal thought or image (Campbell, 2004, p. 312).
  • A true hallucination will be perceived as being in external space, distinct from imagined images, outside conscious control, and as possessing relative permanence. (Oxford Handbook of Psychiatry; Semple, Smyth, Burns, Darjee, & Mclntosh, 2005).
  • A false sensory perception that has a compelling sense of reality despite the absence of an external stimulus. It may affect any of the senses, but auditory hallucinations and visual hallucinations are most common. Hallucination is typically a symptom of psychosis, although it may result from substance abuse or a medical condition, such as epilepsy, brain tumor, or syphillis (APA Dictionary of Psychology; VandenBos, 2007, p. 427).
  • Hallucinations are images based on immediately internal sources of information, which are appraised as if they came from immediately external sources of information (Horowitz, 1975, p. 165).
  • Any percept-like experience which (a) occurs in the absence of the appropriate stimulus, (b) has the full force or impact of the corresponding actual (real) perception, and (c) is not amenable to direct and voluntary control by the experiencer (Slade & Bentall, 1988, p. 23).
  • A sensory experience which occurs in the absence of external stimulation of the relevant sensory organ, but has the compelling sense of reality of a true perception, is not amenable to direct and voluntary control by the experiencer, and occurs in the awake state (Aleman & de Haan, 1998, p. 657).
  • A sensory experience which occurs in the absence of corresponding external stimulation of the relevant sensory organ, has a sufficient sense of reality to resemble a veridical perception, over which the subject does not feel s/he has direction and voluntary control, and which occurs in the awake state (David, 2004, p. 108).

In essence, a hallucination is sensory rather than propositional. Hallucinations are not beliefs about the world around us, they are sensory constructions. Whereas, on the other hand, delusions are about beliefs. This is the primary distinction between hallucinations and delusions.

The Difference Between Delusion And Confabulation

Delusion is commonly defined as a false belief and associated with psychiatric illness like schizophrenia, whereas confabulation is typically described as a false memory and associated with neurological disorder like amnesia – Langdon & Turner, 2009.

Confabulations and delusions are different in numerous ways, but we need to only understand the above simple distinction. Delusions are false beliefs, of which can lead to false memories, while confabulations are indeed false memories.

The Difference Between Delusion And Self-Deception

The difference between delusion and self-deception is controversial for some. The traditional definition of self-deception allowed for greater demarcation between the two because that definition involved the intentional deception of one’s self, irrespective of the facts. However, others provided different accounts of self-deception, of which show the relatedness between delusion and self-deception.

Self-deception can be distinguished in two ways, one is known as straight and the other as twisted self-deception.

In straight self-deception, people are deceived into believing something which they want to be true. For instance, someone can be self-deceived into believing they are smarter than they really are because they want to be incredibly smart.

With twisted self-deception, people are self-deceived into believing something which they want to be false; that is, person p will not want x to be the case, and x won’t be the case, except person p will believe x, regardless. A good example is when a jealous husband believes his wife is cheating, even though in reality she is not.

These are both instances of false beliefs, and would thus seem to fit what delusions are, except there are components missing.

While self-deception can lead to false beliefs, it is entirely feasible that a self-deception can be changed upon a presentation of evidence; whereas, conversely, delusions seldom change, if at all, when counter-evidence is presented.

Another aspect is, though perhaps less relevant, that delusions are often deviant beliefs: uncommon. Of course, self-deceptions can also be deviant, but delusions are usually deviant, whereas many self-deceptions are not: e.g., self-deceptions about intelligence, relationships, or self-worth.

Furthermore, self-deceptions are motivated interpretations about the facts, whereas delusions have little to no concern about the facts. So, both may indeed be distortions about reality, but they have distinct motivations.

So, delusions and self-deceptions are similar insofar as they are both false beliefs about reality, however delusions are distinct because:

  • Delusions usually don’t respond to evidence.
  • Delusions are often deviant beliefs.
  • Delusions are not motivated interpretations of the facts.

Delusions: Philosophy, Psychiatry, and Psychology.

What shall follow is a systematic analysis of the literature on delusions across psychology, psychiatry, and philosophy. Hopefully, at the end, we can grasp firmly the nature of delusions.

What Is The Nature Of A Delusion?

So, we have thus far taken for granted that delusions are beliefs, but we have only done so to have some common understanding on the topic. Most researchers and scholars agree that delusions are, in essence, a belief, and that delusions are not only a belief. Which is to say, there is more to the nature of delusion than just belief.

A traditional view of delusions has been that delusions arise from erroneous logic being applied to perception. That is, because patients hold beliefs which seem to be based on inferences devoid of the evidence, then there has to be some error in the inference process. Put otherwise, delusions are bad inferences, of which are not predicated on data (Bandura, 1963).

Such a view presupposes the validity of a delusional individuals perceptions. That is, other scholars, such as (Maher, 1974), have rightly pointed out that the inference process of delusional individuals can be entirely intact and functioning properly; however, the perceptual processes might be delivering abnormal stimuli.

Another view on delusions has to do with correlations. (Brennan & Hemsley, 1984) believe that delusions come about through illusory correlations rather than abnormal perception or disordered thinking. In their research, patients with schizophrenia perceived stronger illusory correlations than normal populations; and so, delusions are illusory correlations.

These views are limited, however. Each view of delusion espoused so far deals specifically with paranoid delusions, of which always involve some form of inference. There are other delusions that don’t involve any inference what so ever. And these theories fail to account for them.

More specifically, we have the following types of delusions:

  • Delusions Of Reference
  • Delusions Of Control
  • Alien Control
  • Thought Insertion
  • Thought Withdrawal

Delusions of reference are delusional beliefs about other people. For instance, I see someone wearing a hat, I then become of the belief that I should build a spaceship out of hats.

Delusions of control involve the sense that someone or something is responsible for my actions. In example, if I had the belief that some unique and special force is making me type this sentence, then I would be experiencing a delusion of control.

Alien control is another delusion which isn’t about inference; that is, patients with alien control delusions feel as though aliens were controlling their minds. It isn’t something which is inferred, but rather passively experienced.

Similarly, thought insertion and thought withdrawal are also experiential rather than inferential. One refers to the passive experience of feeling as though someone were stealing their thoughts, while the other refers to the passive experience of feeling as though someone were inserting thoughts.

Theories Of Delusion

We have already discussed a few theories of delusions: namely,

  1. The Inferential Theory Of Delusions
  2. The False Perception Theory Of Delusions
  3. The Illusory Correlation Theory Of Delusions

But there are  more theories of delusions to be discussed: namely,

  1. The Deficit In Central Monitoring Theory Of Delusions
  2. The Imagination Theory Of Delusions
  3. The Desire Theory Of Delusions
  4. The Middle State Theory Of Delusions

(note: these names are not used elsewhere, I have simply used them for convenience).

Frith, in the cognitive neuropsychology of schizophrenia, believes that some delusions are not at all beliefs. He believes, for example, that because patients can identify thoughts which are not their own that there then has to be some mechanism responsible for the identification for our own thoughts. Thus, when such a mechanisms malfunctions, we have the experience of thoughts being external or alien.

Likewise, Frith also believes there is some mechanisms responsible for the identification of our own actions and our own intentions. And so, when said mechanisms malfunction, we then experience our actions as being external or alien and lack awareness of our own intention to act.

The lack of self-monitoring can explain how patients experience alien control, external control of action, or thought insertion. The inability to identify these as their own thoughts, actions, and etc., are what lead them to perceive as coming from someone or something else.

Comparatively, (Currie G., 2000) says the following:

“…the disorder of imagination theory, the schizophrenic patient does not have a problem formulating thoughts of the form S thinks that P; he or she has a problem distinguishing between merely imagining some proposition and really believing it.” – (Currie, 2000, p. 7).

So, a patient might imagine martians, except the patient fails to recognize that the content of their imagination is not a belief. And so, they will believe in martians due to a failure in their ability to recognize their own imaginative content as being distinct from beliefs.

As currie points out, a lack of self-awareness need not entail belief, which means Frith’s account has some problems. Not only that, but currie likewise points out patients who have delusional beliefs, yet have self-awareness nevertheless.

Another account of delusions (Egan, 2009) is the desire theory. Such a view believes that delusions are in-between desires and beliefs. That we don’t strictly have beliefs or desire, but a mix between the two, when we are in possession of a delusion. This is because delusions often lack the same inferential power which an ordinary belief would have: e.g., if we believe X has become a hat, we don’t incorporate the more basic notion that people can become hats into our worldview. It is a fragmented and isolated belief. Thus lacking important features of beliefs (among other arguments in his paper).

Likewise, delusions, if they stem from imagining, are not based on evidence. If that is so, then why do we bring up such imaginings? Egan’s believes this has something to do with desires. Thus, for Egan’s, delusions are a mix between desires and beliefs.

The final and last theory we will discuss is the middle state theory of delusions. This theory effectively treats delusions as being on a scale. On the one hand, we have beliefs, and on the other hand, we have no belief. Delusions are somewhere in-between being a belief and a non-belief. In example, patients can believe their doctors have poisoned their food, yet eat it regardless, as though the belief weren’t something they “believed”.

“…delusion are, at least sometimes (when the functional role or dispositional profile is weird enough), cases in an in-betweenish gray zone—not quite belief and not quite failure to believe”  – (Schwitzgebel, 2012, p. 3).

To sum up, then. Delusions are argued to be one of the following: beliefs, passive experiences, or imaginative content which we form beliefs about. We can throw these different conceptualizations of delusions into two broad categories: namely, motivational and deficit theories (McKay et al., 2007). The motivational views believe delusions to be instances of deliberate self-deception (Bortolotti et al., 2012), while the deficit theories view delusions as faulty belief mechanisms.

Delusions, Beliefs, And Folk-Psychology

Some theorists believe that delusions are not beliefs at all: “delusions are empty speech-acts that disguise themselves as beliefs” (1996).  So, clearly, there is a lot of debate about whether delusions are beliefs or not. And there are some who believe that such a debate has problems: namely, (Porcher, 2018) believes, “the first problem [is] the legitimacy of the debate itself. [And] the second problem [is] about the legitimacy of the claims being made…”

Numerous people have questioned whether the current debate is strictly about terminology or if there is more being said about the ontology of the things being discussed. Since many of the theories are attempts to either deny or propose the plausibility of labeling delusions as beliefs, it appears that the current literature is primarily focused on finding a proper term. That is, whether the term accurately characterized the evidence or not, which is different than attempting to establish a means to explain and understand the evidence insofar as we are less concerned with the thing-itself.

Furthermore, some have questioned the ability fo our folk-psychological categories to accurately describe all that is labelled as delusion. It might very well be the case that delusions cannot be elucidated by one single phenomenological category.

And in addition, the question of “what a delusion is” seems to be less important than the questions of, “what caused the delusion,” or,”how does the delusion impact normal functioning”.

Lastly, some researchers and authors have argued that we ought let cognitive neuropsychiatry determine the essence of something. It is from brain studies that we should start; only because doing so, they believe, brings about less ambiguity. Although, this nevertheless requires some empirical support, which was not provided in (Porcher, 2018).

So, the debate between whether delusions are beliefs or not can get lost in philosophy, since the purpose is not to debate the metaphysics of belief, which much of the literature has done. Likewise, there needs to be a point wherein which we consider the limitations upon our introspective categories to accurately describe all instances of delusion.

What Makes Delusions Pathological?

Bortolotti, L. (2010) argues that delusions are on an extreme end of a spectrum of beliefs. More specifically, on the one end, we have hyper-irrational beliefs (delusions), while on the other hand, we have hyper-rational beliefs (veridical beliefs). Of course, not all irrational beliefs are delusions, according to Bortolotti. She believes that delusions and irrational beliefs can both share a deficit in three necessary standards for rationality: procedural, agential, and epistemic.

Procedural rationality is in reference to the ability of a belief to cohere and integrate with other beliefs. Delusions often lack an ability to cohere or integrate with other beliefs.

Epistemic rationality is in reference to the ability of a belief to be about, or correspond to, evidence. Delusions, as already said before, seldom abide by the norms of evidence.

Agent rationality is in reference to the relationship between a belief and an action, and how some behaviours are a representation of a belief in some proposition. Delusions, notably, lack this quality. But again, so do irrational beliefs more generally.

So, Bortolotti believes both delusions and irrational beliefs share similar characteristics; therefore, what makes a delusion pathological is more than its apparent irrationality. But as Petrolini, V. (May 19, 2017) points out:

…if delusions cannot be distinguished from other irrational beliefs by their failure to live up to rational norms, then what makes delusions pathological?

Bortolotti attempts to suppose that delusions are distinct insofar as they cause great distress to their patients. This is a general mark of most mental illnesses – that they cause the patient distress in life – but it does not distinguish delusions from irrational beliefs. There are instances of irrational beliefs which can cause people great distress. For example, my irrational belief that monsters live underneath my bed is incredibly distressing and likewise non-delusional. Even furthermore, rational beliefs can also cause someone distress. So, this is insufficient for demarcation between delusions and irrational beliefs.

Now, Petrolini has a proposal for how to demarcate delusions from irrational beliefs; namely, relevance detection. This device essentially functions as a filter to focus attention onto something specific while disregarding the irrelevant information. It is guided by the context and goals which a person finds themselves in; for example, when I am reading a book, I give no attention to the background content which sits, above and behind the cover of the book, in my environment. Instead, my attention is, by virtue of my goal to read the words jotted upon the paper, focused entirely on the pages: those words are what is most relevant.

And the relevance detection mechanism(s) are proliferated throughout agent, epistemic, and procedural rationality; which is to say, each norm of rationality requires some means to determine the relevancy within. For instance, a person has to determine the relevant portions of their beliefs to act on, a person has to determine relevant portions of evidence, and a person has to determine the relevant ways in which a belief influences other beliefs. This effectively gives us numerous points of reference that the relevancy mechanism(s) have to act on.

From here, he argues that relevance is guided by emotional salience; which is to say, whether we become alert to a particular feature or object depends, in part, by its emotional salience: e.g., we notice sharp teeth on animals because of the danger they present – danger is often associated with high emotional arousal. It is his belief that the relevance mechanisms are, in delusional patients, hijacked by emotional disturbances:

…in delusional cases this attribution of emotional significance appears importantly misplaced: seeing that a particular lamp-post is unlit, hearing a dog barking, or noticing that one’s partner ties his shoes differently are causes of deep emotional turmoil.

Thus, what makes a delusion pathological is not the particular content, nor the means by which the belief was formed. Rather, delusions are pathological because of a deficit in cognitive relevance.

Conclusion On Delusions

In due time, I am certain there will be more disagreements about how to categorize delusions, as well as disagreements about identifying what counts a delusion. And this is, I believe, not a problem. Comparatively speaking, It would be dangerous for us to adopt a position of certainty within our beliefs, due to reasons espoused in the munchausen trilemma article I wrote.

What should matter is whether our newer models can predict and explain with greater efficacy or not. If not, then we should keep the older models until the newer ones can predict or explain in some better fashion the contents under study.

Each theory of delusions put forth herein has its own merits and explanatory power, and each theory of delusions put forth likewise fails to characterize some variant of delusions. It seems delusions are anything but heterogenous; therefore, multiple theories might very well be warranted in explaining delusions.


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Ideasinhat is a business development analyst and longtime reader of academic literature. He writes books and essays on science and philosophy, and posts them to this website. The essays, as with the books, cover topics from psychology, philosophy, and cognitive science to economics, politics, and law.

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