- Email: [email protected]
Delusions: Analysis and criteria
Delusions: Analysis and Criteria James
H. Moor
and Gary J. Tucker
HAT CRITERIA should we use in identifying delusions? The question is important since the concept of a delusion figures prominently in many diagnostic schemes. 1*2,3Moreover, the way in which the concept of a delusion is applied can have significant implications for society. For example, whether or not a person is considered competent to stand trial or is found not guilty by reason of insanity may depend upon whether or not it can be established that he is delusional. In another context. repressive political actions in the name of medical treatment may be carried out on the grounds that deviance in political viewpoint should be regarded as delusional thinking. Obviously, how we understand what a delusion is can have important consequences. Consider the following statements: (1) A physician believes that it’s his destiny to serve mankind and that he has been specially chosen for this: (2) A woman believes that her neighbor is trying to poison her by spraying poison into her house late at night; (3) A man believes that his thoughts are capable of destroying people: (4) A devoutly religious person believes that God spoke to him and told him to spend the rest of his life working for God and the church; (5) An early 16th-century scientist believes that the earth revolves around the sun: (6) An embassy worker believes that his office is being bombarded with microwaves that are making him sick, and (71 A Russian believes there is a better form of government than the one currently existing in the USSR. To what extent do these statements describe delusions’? What further information. if any, is needed to decide whether a delusion is occurring in each case? It is the intent of this paper to propose some criteria for identifying delusions. but it is necessary to begin by pointing to some of the defects in standard accounts of delusions. Standard definitions of “delusion” often emphasize such factors as having a fcrlsr belief or having a deviant boliqf. For example, the APA glossary defines a delusion as, “A false belief out of keeping with the individual’s level of knowledge and his cultural group.“” In the Conzprehensir~e Te.rtbm.4 c?f’ Psychiatry (ed 31, we find, “A delusion is a false belief that arises without appropriate external stimulation and that is maintained unshakably in the face of reason. Furthermore, the belief held is not one ordinarily shared by other members of the patient’s socio-cultural and educational group.“” Redlich and Freedman state “Delusions are incorrigible false beliefs that are not shared or From the Department of Philosophy. Drrrtmouth College, trnd the Deptrrtment of P~vchiutr~. Dartmouth Medico/ School. Hunover, N.H. James H. Moor, Ph.D.: Associate Prqfessor ofPhilosophy. Dartmouth College: Gary J. Tucker. M.D.: Professor of Psychiatry. Dartmorrth Medicul School, Hanover, New Htrmpshire. The material in this poper is the product of a ,firculty semincrr clt Dartmouth thnt included the .following members of the Departments of Philosophy. P.cychiutry, and Religion: Berncrrd Bergen. Ph.D.. K. Dunner Clouser. Ph.D. (Department of Humanities. College of Medicien. Hershe> Medical Center), Charles Culver, M.D.. Ph.D.. Bernnrd Gert. Ph.D., RonaldGreen. Ph.D.. Stclnle! Rosenberg. Ph.D., Joel Rudinow, Ph.D. and Peter Whybrow. M.D. 0 1979 by Grune & Stratton, Inc. 0016440X1791-7004-0011$01.00l0
388
Comprehensive Psychiatry,
Vol. 20, No. 4 (July/August),
1979
DELUSIONS:
ANALYSIS
AND CRITERIA
389
sanctioned by a group.“6 Perhaps the most extensive phenomenologic discussion of delusions is that by Karl Jaspers in his monumental text, General Psychopathology. Jaspers defines a delusion similar to the above definitions as a false “judgment” but qualifies this definition with the following characteristics: (1) It is held with extraordinary conviction; (2) It is impervious to other experiences and compelling counter-arguments; and (3) the content is impossible.7 WHAT A DELUSION IS NOT The False Belief View It is tempting to characterize a delusion as a false belief. After all, it can be argued that if somebody has a false belief, then he is not completely in contact with reality; and if somebody has a true belief, then at least on that matter he is in touch with reality. But if the concept of a delusion is to have a vital role in psychiatry, there are serious difficulties with regarding a false belief as either a sufficient or a necessary condition for a delusion. If having a false belief were a sufficient condition for having a delusion, then since most, if not all of us, hold some false beliefs, most, if not all of us, would be delusional. This understanding of a delusion makes it useless as a psychiatric category. We want the diagnosis that a patient is delusional to have some medical significance. In part, such a diagnosis will usually suggest that the patient requires treatment. To say that someone has a false belief may mean nothing more than the person is ignorant or has made a simple mistake-a condition often easily corrected by providing the appropriate information. The occurrence of false beliefs, particularly unusual ones, may be taken as a sign of a delusion but it should not be regarded as a defining condition. Otherwise, a physician could rid a patient of paranoia by persecuting him. The Deviant Belief View Another common understanding of delusions is to characterize them as deviant beliefs. Under this view, a person has a delusion on the grounds that the belief is not held by the majority. This view is appealing initially since one can identify for any given group which beliefs are delusional and which are not, merely by determining which beliefs are held by the majority. The view becomes much less appealing once one considers the difficulty in picking the “right” group as the reference class. If a psychiatrist walks on a ward that has twenty patients each of whom believes that physicians are persecuting them, then the psychiatrist, who presumably does not believe this, holds a deviant belief; but he does not have a delusion. Even if one considers the whole society or culture (however that is to be defined), to be the proper reference class, it still may be the case that deviant beliefs and delusions are not closely connected. For instance, imagine a society in which one scientist carefully works out a new theory on the basis of well-examined evidence. If the scientist is the only one to believe his theory in that society, then his beliefs are deviant; but his beliefs may well reflect a much better grasp of reality than those of the other members of society. Since it is possible for a majority view to be delusional*
MOOR AND TUCKER
390
and a minority view to be nondelusional, having a deviant belief is not a promising candidate as a necessary or a sufficient condition for having a delusion. A further distressing consequence of the deviant belief view is that it helps legitimize the use of psychiatric treatment for political repression against minorities with dissenting opinions. WHAT
A DELUSION
IS
We believe that a delusion is a belief that a person has although he has (or at least has been presented with) considerable evidence against the belief. and comparatively little or no evidence for it. He has the ability to evaluate this kind of evidence. and he would maintain the belief even if given ample opportunity and incentive to evaluate the evidence. This definition can be thought of ah having four parts. A person has a delusion if and only if (1) the person has ;I belief: (2) the person has (or at least has been presented with) considerable evidence against the belief, and comparatively little or no evidence for it; (3) the person has the ability to so evaluate this kind of evidence; and (4) he would maintain the belief even if given ample opportunity and incentives to evaluate the evidence. Let us consider these four conditions separately. The Person
Hers (I Beliqf
To suggest that delusions involve beliefs is not a very controversial claim. Even the characterizations of delusions just discussed-the false belief view and the deviant belief view-treat delusions as beliefs. It is quite natural to explain that a patient has a delusion of persecution in that he has the he/ie,f’thar others are “out to get him.” A patient has delusions of grandeur only if he has certain peculiar heliqfk about his own importance. Nevertheless, it is worthwhile to stress that it is the beliefs that a person has that make him delusional and not simply his sensations or feelings. even though his sensations or feelings may be misleading. For example. a patient who has had his leg amputated may still have the sensation of having a leg. The patient who experiences this phantom limb phenomenon is having a hallucination but is not necessarily suffering from a delusion. The patient may kinesthetically feel as if he still has his leg although he helie,ves quite correctly on the basis of his own observations and perhaps the physician’s account of the operation that he has had the leg amputated. On the other hand, if the patient believes that he must still have his leg while realizing that he cannot see it or touch it and knowing that the physician has assured him that his leg has been amputated, then he is indeed suffering from a delusion. The Person Hers (or crt Least Hn.v Been Presented With) Considernhle Against the Beliqf nnd Cornpnrlrtively Little or No E\lidence .for It
E\idence
The best a rational agent can do is to make judgments about the world on the basis of the evidence he has acquired. Thus, a little girl who believes in a tooth fairy holds a false belief and probably a deviant one. but she is not suffering from a delusion in this belief. Given that her parents readily confirm the existence of the tooth fairy and, just as predicted, in the morning the girl finds coins under her pillow where only baby teeth had been the night before. it is
DELUSIONS:
ANALYSIS
AND CRITERIA
391
perfectly rational for the little girl to believe in the existence of the tooth fairy. It would, however, be delusional for an adult to believe in the existence of the tooth fairy if she has the ordinary evidence that the parents replace baby teeth with money. When a person is suspected of having a delusion, it is in part because the person is suspected of holding the belief in spite of the considerable evidence that person has against it. Notice that such a suspicion evaporates whenever it can be shown that the person has not been presented with considerable evidence against the belief or the person has good evidence for the belief. For example, it may seem to us delusional for an alchemist to use his methods to convert lead into gold, but given his lack of knowledge against the possibility it is not delusional. It is the evidence available to the person that counts. Darwin’s deviant belief in evolution may have initially seemed delusional to others, but given the evidence he had acquired for it from his voyages, it was not delusional. The Person Has the Ability to So Evaluate
This Kind of Evidence
A stipulation about the person’s ability must be made because evidence does not always make its force manifest without appropriate interpretation. Suppose a nonengineer believes that a bridge will not collapse although he has seen data that indicated that the bridge will surely collapse. If the data are such that only a trained engineer could properly interpret them, then the person holds a belief for against which he has acquired considerable evidence, but he does not thereby have a delusion since he lacks the ability to evaluate the evidence. On the other hand, if the person had acquired the evidence, had the ability, incentive, and opportunity to evaluate it, and still believed the bridge would not collapse, then he would have a delusion. To say a person has the ability to evaluate the evidence means he can evaluate that kind of evidence, although he may not be properly evaluating such evidence in a particular situation. Thus, if a person has an impairment of the central nervous system, he may lack normal abilities (even abilities he once had) to make certain kinds of discriminations. For instance, some patients with anosognosia who believe that an obviously paralyzed limb is not paralyzed may well lack the ability to evaluate the kind of evidence relevant to the belief. Mistaken beliefs resulting from disabilities are not regarded as delusions. However, if a person has the ability to process certain kinds of information, but does not utilize this ability even when given ample opportunity and motivation, then his beliefs may well be delusional. For instance, somebody who can identify doctors, nurses, and patients, and can recognize operation wounds, but who denies he has had an operation even when shown his operation wound by doctors and nurses, is a person suffering from a delusion. The Person Would Maintain the Belief Even if Given Amp/e Opportunity and Incentives to Evaluate the Evidence To see why this condition is necessary, consider a situation in which a person has records of income and the ability to evaluate these records. Suppose such an evaluation would convince him that he will not receive a large tax return.
MOOR AND TUCKER
392
Nevertheless, this person believes he will receive a large tax return because he has not taken the opportunity to evaluate the evidence. If the person would readily change his belief about the size of his tax return after such an evaluation (given an opportunity and perhaps the incentive of an approaching deadline to file his return), then his original belief may have been optimistic but it was not delusional. Delusions are firmly held beliefs that would be maintained even after motivated and lengthy assessment of the evidence. APPLICATION TO PSYCHIATRY The analysis of delusions given in the last section applies to the classical psychiatric syndromes. If a patient believes he is being persecuted, then he has a delusion if and only if he has considerable evidence against this belief and comparatively little or no evidence for it, he has the ability to evaluate the evidence, and he would continue to believe in his persecution even if given ample opportunity and incentive to evaluate the evidence. Similarly, a person has a delusion of grandeur if and only if he has a belief about his own selfimportance for which he has considerable evidence against and comparatively little or no evidence for and he has the ability to evaluate the evidence, and would continue to believe in his self-importance even if given ample opportunity and incentive to evaluate the evidence. In applying these criteria in psychiatric contexts, it is very important to distinguish between a patient’s feelings and beliefs. Take the case of a .50-yearold bank president who for the past 3 months has noted increased insomnia. weight loss, and feelings of sadness. He consults a psychiatrist and states that he feels worthless, his life has amounted to nothing, and that in truth he is a failure. Does he have a delusion? To evaluate this we would need to know the following: Are these beliefs about his actual accomplishments or are these reports of his feelings? If on questioning about this the patient says, “I know this is strange because for all intents and purposes the world would say I am a great success-my bank is the largest and most successful in the area; I have been promoted very rapidly and been given large bonuses every year by the director etc., but yet I do not feel happy, satisfied or fulfilled.” then we would probably conclude that the initial statement was not a report of a delusional belief but of a feeling state. On the other hand, suppose the patient believes that he is a failure in terms of traditional standards of success in business. Then it becomes an issue of his evidence and his ability to evaluate it. If we determine that his cognitive functions are intact and we confront him with bank reports and colleagues, all of whom attest to great success of the bank and his administration of it, but he still maintains his belief in his failure. then we would consider the revelant beliefs to be delusional. CONCLUSIONS At the beginning of this paper, we listed a series of beliefs and asked which were examples of delusions. The best response to this query is to note that merely knowing about a belief does not provide enough information on which to make a good judgment about whether or not it is a delusion. Even if one is told that a particular belief is false or deviant, it is still not enough of a basis on
DELUSIONS:
ANALYSIS
AND CRITERIA
393
which to make a good judgment. One must know something about the person’s evidence relating to the belief and the person’s abilities for evaluating the evidence. Of course, if the belief is very deviant or obviously false one might be very suspicious that a delusion does exist since one assumes normal sorts of evidence and normal sorts of abilities. If a woman believes that her neighbor is trying to poison her by spraying poison into her house at night, then this belief is eccentric enough that one would suppose the woman is delusional. Nevertheless, it could be the case, as it often is in suspense movies, that the woman has indeed a great deal of evidence that her neighbor is trying to poison her by spraying poison into her home at night. In such a case she would certainly not be delusional and would be quite rightfully upset. The advantage of our analysis of delusion is that it suggests the crucial factors one must consider in identifying delusions. These evidential factors are at least implicit in the relevant standard medical syndromes and are the relevant factors for which to be alert in cases that do not fall under the standard medical syndromes. Obviously, there are borderline cases that are difficult to classify but these will be the very cases in which the factors we have stressed will be uncertain. In stating the criteria for delusions we have not attempted to provide a causal theory for delusions. Our analysis is neutral with respect to any number of theories that might account for the occurrence of delusional thinking. Moreover, it is a mistake to think, as Kolbg apparently does, that one must provide such a theory in order to define delusions. Just as one can identify a cancer without understanding its causes, one can identify a delusion without understanding its causes. Another feature of our analysis is that delusions are made relative in just the right way. Delusions are relative to the evidential situation and abilities of the person. Thus, it does not follow that somebody who holds a false religious view or a deviant scientific opinion must be automatically classified as delusional. One must take into account the person’s experiences, intelligence, and education. On the other hand, relative to the evidential factors, some beliefs held by some persons definitely do count as delusional. The concept of delusion thus understood becomes a useful concept for psychiatric theory and practice. REFERENCES
1. Feighner JP, Robins E, Guze SB, et al: Diagnostic criteria for psychiatric research. Arch Gen Psychiatry 26:57-63. 1972 2. American Psychiatric Association: Diagnostic and Statistical Manual III. Washington, D.C., 1978 3. Wing JK, Cooper JE, Sartorius N: Description and Classification of Psychiatric Symptoms. Cambridge, Cambridge University Press, 1974 4. American Psychiatric Association: A Psychiatric Glossary. Washington, D.C., 1964, P 24 5. Freedman A, Kaplan H. Sadock B:
Comprehensive Textbook of Psychiatry (ed 2). Baltimore, Williams & Wilkins, 1975. pp 792793 6. Redlich F, Freedman D: The Theory and Practice of Psychiatry. New York, Basic Books, 1966, p 106 7. Jaspers K: General Psychopathology (ed 7). Manchester, Manchester University Press, 1962, pp 95-96 8. Mackay C: Extraordinary Popular Delusions. Vermont, Fraser, Wells, 1963 9. Kolb L: Modern Clinical Psychiatry. Philadelphia, Saunders, 1977, p 94
H. Moor
and Gary J. Tucker
HAT CRITERIA should we use in identifying delusions? The question is important since the concept of a delusion figures prominently in many diagnostic schemes. 1*2,3Moreover, the way in which the concept of a delusion is applied can have significant implications for society. For example, whether or not a person is considered competent to stand trial or is found not guilty by reason of insanity may depend upon whether or not it can be established that he is delusional. In another context. repressive political actions in the name of medical treatment may be carried out on the grounds that deviance in political viewpoint should be regarded as delusional thinking. Obviously, how we understand what a delusion is can have important consequences. Consider the following statements: (1) A physician believes that it’s his destiny to serve mankind and that he has been specially chosen for this: (2) A woman believes that her neighbor is trying to poison her by spraying poison into her house late at night; (3) A man believes that his thoughts are capable of destroying people: (4) A devoutly religious person believes that God spoke to him and told him to spend the rest of his life working for God and the church; (5) An early 16th-century scientist believes that the earth revolves around the sun: (6) An embassy worker believes that his office is being bombarded with microwaves that are making him sick, and (71 A Russian believes there is a better form of government than the one currently existing in the USSR. To what extent do these statements describe delusions’? What further information. if any, is needed to decide whether a delusion is occurring in each case? It is the intent of this paper to propose some criteria for identifying delusions. but it is necessary to begin by pointing to some of the defects in standard accounts of delusions. Standard definitions of “delusion” often emphasize such factors as having a fcrlsr belief or having a deviant boliqf. For example, the APA glossary defines a delusion as, “A false belief out of keeping with the individual’s level of knowledge and his cultural group.“” In the Conzprehensir~e Te.rtbm.4 c?f’ Psychiatry (ed 31, we find, “A delusion is a false belief that arises without appropriate external stimulation and that is maintained unshakably in the face of reason. Furthermore, the belief held is not one ordinarily shared by other members of the patient’s socio-cultural and educational group.“” Redlich and Freedman state “Delusions are incorrigible false beliefs that are not shared or From the Department of Philosophy. Drrrtmouth College, trnd the Deptrrtment of P~vchiutr~. Dartmouth Medico/ School. Hunover, N.H. James H. Moor, Ph.D.: Associate Prqfessor ofPhilosophy. Dartmouth College: Gary J. Tucker. M.D.: Professor of Psychiatry. Dartmorrth Medicul School, Hanover, New Htrmpshire. The material in this poper is the product of a ,firculty semincrr clt Dartmouth thnt included the .following members of the Departments of Philosophy. P.cychiutry, and Religion: Berncrrd Bergen. Ph.D.. K. Dunner Clouser. Ph.D. (Department of Humanities. College of Medicien. Hershe> Medical Center), Charles Culver, M.D.. Ph.D.. Bernnrd Gert. Ph.D., RonaldGreen. Ph.D.. Stclnle! Rosenberg. Ph.D., Joel Rudinow, Ph.D. and Peter Whybrow. M.D. 0 1979 by Grune & Stratton, Inc. 0016440X1791-7004-0011$01.00l0
388
Comprehensive Psychiatry,
Vol. 20, No. 4 (July/August),
1979
DELUSIONS:
ANALYSIS
AND CRITERIA
389
sanctioned by a group.“6 Perhaps the most extensive phenomenologic discussion of delusions is that by Karl Jaspers in his monumental text, General Psychopathology. Jaspers defines a delusion similar to the above definitions as a false “judgment” but qualifies this definition with the following characteristics: (1) It is held with extraordinary conviction; (2) It is impervious to other experiences and compelling counter-arguments; and (3) the content is impossible.7 WHAT A DELUSION IS NOT The False Belief View It is tempting to characterize a delusion as a false belief. After all, it can be argued that if somebody has a false belief, then he is not completely in contact with reality; and if somebody has a true belief, then at least on that matter he is in touch with reality. But if the concept of a delusion is to have a vital role in psychiatry, there are serious difficulties with regarding a false belief as either a sufficient or a necessary condition for a delusion. If having a false belief were a sufficient condition for having a delusion, then since most, if not all of us, hold some false beliefs, most, if not all of us, would be delusional. This understanding of a delusion makes it useless as a psychiatric category. We want the diagnosis that a patient is delusional to have some medical significance. In part, such a diagnosis will usually suggest that the patient requires treatment. To say that someone has a false belief may mean nothing more than the person is ignorant or has made a simple mistake-a condition often easily corrected by providing the appropriate information. The occurrence of false beliefs, particularly unusual ones, may be taken as a sign of a delusion but it should not be regarded as a defining condition. Otherwise, a physician could rid a patient of paranoia by persecuting him. The Deviant Belief View Another common understanding of delusions is to characterize them as deviant beliefs. Under this view, a person has a delusion on the grounds that the belief is not held by the majority. This view is appealing initially since one can identify for any given group which beliefs are delusional and which are not, merely by determining which beliefs are held by the majority. The view becomes much less appealing once one considers the difficulty in picking the “right” group as the reference class. If a psychiatrist walks on a ward that has twenty patients each of whom believes that physicians are persecuting them, then the psychiatrist, who presumably does not believe this, holds a deviant belief; but he does not have a delusion. Even if one considers the whole society or culture (however that is to be defined), to be the proper reference class, it still may be the case that deviant beliefs and delusions are not closely connected. For instance, imagine a society in which one scientist carefully works out a new theory on the basis of well-examined evidence. If the scientist is the only one to believe his theory in that society, then his beliefs are deviant; but his beliefs may well reflect a much better grasp of reality than those of the other members of society. Since it is possible for a majority view to be delusional*
MOOR AND TUCKER
390
and a minority view to be nondelusional, having a deviant belief is not a promising candidate as a necessary or a sufficient condition for having a delusion. A further distressing consequence of the deviant belief view is that it helps legitimize the use of psychiatric treatment for political repression against minorities with dissenting opinions. WHAT
A DELUSION
IS
We believe that a delusion is a belief that a person has although he has (or at least has been presented with) considerable evidence against the belief. and comparatively little or no evidence for it. He has the ability to evaluate this kind of evidence. and he would maintain the belief even if given ample opportunity and incentive to evaluate the evidence. This definition can be thought of ah having four parts. A person has a delusion if and only if (1) the person has ;I belief: (2) the person has (or at least has been presented with) considerable evidence against the belief, and comparatively little or no evidence for it; (3) the person has the ability to so evaluate this kind of evidence; and (4) he would maintain the belief even if given ample opportunity and incentives to evaluate the evidence. Let us consider these four conditions separately. The Person
Hers (I Beliqf
To suggest that delusions involve beliefs is not a very controversial claim. Even the characterizations of delusions just discussed-the false belief view and the deviant belief view-treat delusions as beliefs. It is quite natural to explain that a patient has a delusion of persecution in that he has the he/ie,f’thar others are “out to get him.” A patient has delusions of grandeur only if he has certain peculiar heliqfk about his own importance. Nevertheless, it is worthwhile to stress that it is the beliefs that a person has that make him delusional and not simply his sensations or feelings. even though his sensations or feelings may be misleading. For example. a patient who has had his leg amputated may still have the sensation of having a leg. The patient who experiences this phantom limb phenomenon is having a hallucination but is not necessarily suffering from a delusion. The patient may kinesthetically feel as if he still has his leg although he helie,ves quite correctly on the basis of his own observations and perhaps the physician’s account of the operation that he has had the leg amputated. On the other hand, if the patient believes that he must still have his leg while realizing that he cannot see it or touch it and knowing that the physician has assured him that his leg has been amputated, then he is indeed suffering from a delusion. The Person Hers (or crt Least Hn.v Been Presented With) Considernhle Against the Beliqf nnd Cornpnrlrtively Little or No E\lidence .for It
E\idence
The best a rational agent can do is to make judgments about the world on the basis of the evidence he has acquired. Thus, a little girl who believes in a tooth fairy holds a false belief and probably a deviant one. but she is not suffering from a delusion in this belief. Given that her parents readily confirm the existence of the tooth fairy and, just as predicted, in the morning the girl finds coins under her pillow where only baby teeth had been the night before. it is
DELUSIONS:
ANALYSIS
AND CRITERIA
391
perfectly rational for the little girl to believe in the existence of the tooth fairy. It would, however, be delusional for an adult to believe in the existence of the tooth fairy if she has the ordinary evidence that the parents replace baby teeth with money. When a person is suspected of having a delusion, it is in part because the person is suspected of holding the belief in spite of the considerable evidence that person has against it. Notice that such a suspicion evaporates whenever it can be shown that the person has not been presented with considerable evidence against the belief or the person has good evidence for the belief. For example, it may seem to us delusional for an alchemist to use his methods to convert lead into gold, but given his lack of knowledge against the possibility it is not delusional. It is the evidence available to the person that counts. Darwin’s deviant belief in evolution may have initially seemed delusional to others, but given the evidence he had acquired for it from his voyages, it was not delusional. The Person Has the Ability to So Evaluate
This Kind of Evidence
A stipulation about the person’s ability must be made because evidence does not always make its force manifest without appropriate interpretation. Suppose a nonengineer believes that a bridge will not collapse although he has seen data that indicated that the bridge will surely collapse. If the data are such that only a trained engineer could properly interpret them, then the person holds a belief for against which he has acquired considerable evidence, but he does not thereby have a delusion since he lacks the ability to evaluate the evidence. On the other hand, if the person had acquired the evidence, had the ability, incentive, and opportunity to evaluate it, and still believed the bridge would not collapse, then he would have a delusion. To say a person has the ability to evaluate the evidence means he can evaluate that kind of evidence, although he may not be properly evaluating such evidence in a particular situation. Thus, if a person has an impairment of the central nervous system, he may lack normal abilities (even abilities he once had) to make certain kinds of discriminations. For instance, some patients with anosognosia who believe that an obviously paralyzed limb is not paralyzed may well lack the ability to evaluate the kind of evidence relevant to the belief. Mistaken beliefs resulting from disabilities are not regarded as delusions. However, if a person has the ability to process certain kinds of information, but does not utilize this ability even when given ample opportunity and motivation, then his beliefs may well be delusional. For instance, somebody who can identify doctors, nurses, and patients, and can recognize operation wounds, but who denies he has had an operation even when shown his operation wound by doctors and nurses, is a person suffering from a delusion. The Person Would Maintain the Belief Even if Given Amp/e Opportunity and Incentives to Evaluate the Evidence To see why this condition is necessary, consider a situation in which a person has records of income and the ability to evaluate these records. Suppose such an evaluation would convince him that he will not receive a large tax return.
MOOR AND TUCKER
392
Nevertheless, this person believes he will receive a large tax return because he has not taken the opportunity to evaluate the evidence. If the person would readily change his belief about the size of his tax return after such an evaluation (given an opportunity and perhaps the incentive of an approaching deadline to file his return), then his original belief may have been optimistic but it was not delusional. Delusions are firmly held beliefs that would be maintained even after motivated and lengthy assessment of the evidence. APPLICATION TO PSYCHIATRY The analysis of delusions given in the last section applies to the classical psychiatric syndromes. If a patient believes he is being persecuted, then he has a delusion if and only if he has considerable evidence against this belief and comparatively little or no evidence for it, he has the ability to evaluate the evidence, and he would continue to believe in his persecution even if given ample opportunity and incentive to evaluate the evidence. Similarly, a person has a delusion of grandeur if and only if he has a belief about his own selfimportance for which he has considerable evidence against and comparatively little or no evidence for and he has the ability to evaluate the evidence, and would continue to believe in his self-importance even if given ample opportunity and incentive to evaluate the evidence. In applying these criteria in psychiatric contexts, it is very important to distinguish between a patient’s feelings and beliefs. Take the case of a .50-yearold bank president who for the past 3 months has noted increased insomnia. weight loss, and feelings of sadness. He consults a psychiatrist and states that he feels worthless, his life has amounted to nothing, and that in truth he is a failure. Does he have a delusion? To evaluate this we would need to know the following: Are these beliefs about his actual accomplishments or are these reports of his feelings? If on questioning about this the patient says, “I know this is strange because for all intents and purposes the world would say I am a great success-my bank is the largest and most successful in the area; I have been promoted very rapidly and been given large bonuses every year by the director etc., but yet I do not feel happy, satisfied or fulfilled.” then we would probably conclude that the initial statement was not a report of a delusional belief but of a feeling state. On the other hand, suppose the patient believes that he is a failure in terms of traditional standards of success in business. Then it becomes an issue of his evidence and his ability to evaluate it. If we determine that his cognitive functions are intact and we confront him with bank reports and colleagues, all of whom attest to great success of the bank and his administration of it, but he still maintains his belief in his failure. then we would consider the revelant beliefs to be delusional. CONCLUSIONS At the beginning of this paper, we listed a series of beliefs and asked which were examples of delusions. The best response to this query is to note that merely knowing about a belief does not provide enough information on which to make a good judgment about whether or not it is a delusion. Even if one is told that a particular belief is false or deviant, it is still not enough of a basis on
DELUSIONS:
ANALYSIS
AND CRITERIA
393
which to make a good judgment. One must know something about the person’s evidence relating to the belief and the person’s abilities for evaluating the evidence. Of course, if the belief is very deviant or obviously false one might be very suspicious that a delusion does exist since one assumes normal sorts of evidence and normal sorts of abilities. If a woman believes that her neighbor is trying to poison her by spraying poison into her house at night, then this belief is eccentric enough that one would suppose the woman is delusional. Nevertheless, it could be the case, as it often is in suspense movies, that the woman has indeed a great deal of evidence that her neighbor is trying to poison her by spraying poison into her home at night. In such a case she would certainly not be delusional and would be quite rightfully upset. The advantage of our analysis of delusion is that it suggests the crucial factors one must consider in identifying delusions. These evidential factors are at least implicit in the relevant standard medical syndromes and are the relevant factors for which to be alert in cases that do not fall under the standard medical syndromes. Obviously, there are borderline cases that are difficult to classify but these will be the very cases in which the factors we have stressed will be uncertain. In stating the criteria for delusions we have not attempted to provide a causal theory for delusions. Our analysis is neutral with respect to any number of theories that might account for the occurrence of delusional thinking. Moreover, it is a mistake to think, as Kolbg apparently does, that one must provide such a theory in order to define delusions. Just as one can identify a cancer without understanding its causes, one can identify a delusion without understanding its causes. Another feature of our analysis is that delusions are made relative in just the right way. Delusions are relative to the evidential situation and abilities of the person. Thus, it does not follow that somebody who holds a false religious view or a deviant scientific opinion must be automatically classified as delusional. One must take into account the person’s experiences, intelligence, and education. On the other hand, relative to the evidential factors, some beliefs held by some persons definitely do count as delusional. The concept of delusion thus understood becomes a useful concept for psychiatric theory and practice. REFERENCES
1. Feighner JP, Robins E, Guze SB, et al: Diagnostic criteria for psychiatric research. Arch Gen Psychiatry 26:57-63. 1972 2. American Psychiatric Association: Diagnostic and Statistical Manual III. Washington, D.C., 1978 3. Wing JK, Cooper JE, Sartorius N: Description and Classification of Psychiatric Symptoms. Cambridge, Cambridge University Press, 1974 4. American Psychiatric Association: A Psychiatric Glossary. Washington, D.C., 1964, P 24 5. Freedman A, Kaplan H. Sadock B:
Comprehensive Textbook of Psychiatry (ed 2). Baltimore, Williams & Wilkins, 1975. pp 792793 6. Redlich F, Freedman D: The Theory and Practice of Psychiatry. New York, Basic Books, 1966, p 106 7. Jaspers K: General Psychopathology (ed 7). Manchester, Manchester University Press, 1962, pp 95-96 8. Mackay C: Extraordinary Popular Delusions. Vermont, Fraser, Wells, 1963 9. Kolb L: Modern Clinical Psychiatry. Philadelphia, Saunders, 1977, p 94