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Volume II

John Locke and Modern Theories of Mental Disorder

by Lovro Savić




Anthony Quinton once famously reflected on “a remarkable fact that philosophers, in a sense the experts on rationality, should have taken so little interest in irrationality.”  Moreover, he made no less interesting a claim that “madness is a subject that ought to interest philosophers; but they have had surprisingly little to say about it.”  However, these implied acts of negligence cannot be attributed to John Locke, who, in his famous masterpiece An Essay Concerning Human Understanding—more than three hundred years ago—“offered an elementary discussion of various mental maladies,” including madness, lunacy, and other kinds of irrationality.  Indeed, with the emergence of philosophy of psychiatry and philosophical psychopathology, Locke’s work on madness was occasionally considered by some interpreters—as indicated by the claims of the American psychiatrist James Phillips and psychologist James Morley that Locke’s theoretical conception of madness offers traces identifiable in certain psychiatric conceptions of mental disorders—namely delusion—suggested, primarily, by the Diagnostic and Statistical Manual of Mental Disorders.  However, despite this occasional and infrequent interest based mainly on the phenomena of delusion, this part of Locke’s work has been mostly overlooked by other scholars and widely excluded from philosophical considerations.  In this paper, I propose to fill this significant gap, to enrich philosophical reflection on Locke’s work, and work to develop an adequate interpretation of his account of mental disorder.  I will try to show that his proposed definition of madness appears to have offered a conceptual basis for the understanding of mental disorder in general, and that it shows certain similarities to what some modern theories of philosophical psychopathology propose nowadays.  After assessing his basic ideas, I will try to argue that, when reconsidered, it is plausible to consider Locke to have anticipated contemporary accounts of mental disorder.  This, in turn, will hopefully be sufficient for an illustration of Locke’s work as a relevant “philosophical resource of psychopathology.” 


Locke on Delusion


At the very beginning of Book II in his Essay, John Locke introduces the concepts of the “idiot” and “madman.”  Locke emphasizes that idiots and madmen are primarily characterized as deficient in terms of mental faculties of reasoning.  This portrayal of the mentally impaired led American psychiatrist James Phillips and psychologist James Morley to conclude that Locke’s definition of madness “prevailed through the ensuing centuries” and “did much to shape an understanding” of the conception of delusion in today’s psychiatric practice.  They justify their rather radical idea with reference to the fourth edition of Diagnostic and Statistical Manual of Mental Disorder (DSM-IV). According to DSM-IV, delusion is defined as a “false belief based on incorrect inference about external reality that is firmly sustained despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary.”  Phillips and Morley discern consistency and derivation of this definition from Locke’s explanation of the madman’s condition as taking “their fancies for realities … by the violence of their imaginations.”  They go even further and suggest that Locke’s definition “was a direct influence” on the conception of delusion in the modern era and thus marks “a continuity from Locke to DSM-IV.”  I will not go into detail and examine reasons for their acceptance of the claim about Locke’s direct influence on the psychiatric conception of delusions, for this would lead us astray to a historical examination of Locke’s work.  However, for the purpose of this paper, the rest of the Phillips and Morley’s claim serves as a suitable starting point for a conclusion that Locke’s notion extends far beyond a mere similarity with theories of delusion.  Thus, in what follows, I will argue that Locke’s theory of madness anticipates two modern philosophical theories of mental disorder in general.


Locke’s Idiots and Madmen


Locke’s Essay can be understood as an attempt to make a detailed presentation of philosophy of the mind, its scope, powers, and limits.  Locke establishes his analysis and his understanding of the mind within an empiricist view, which begins from a position that humans are born with minds lacking any innate concepts and ideas.  This view is best illustrated by Locke’s well-known notion of tabula rasa, according to which our initially blank mind is gradually supplied with ideas through life as enabled through our sensory experience.  However, contrary to the rejection of innateness of any ideas, Locke affirms that our knowledge of the world is not only mediated by our sensory experience but also by our innate mental capacities of mind and reasoning.  He distinguishes several of these capacities or faculties of mind, including: perception, retention, discerning, comparing, composition, enlarging, and the abstraction of ideas—which eventually manifest in “quickness of parts,” invention, fancy, and reasoning.  In the early stage of his Essay, Locke was aware that his detailed philosophy of mind could reveal failures of the mind, weaknesses, and a lack of any of the above-mentioned mental faculties. 


Thus, in his Essay, Locke attributes to idiots and madmen a lack of knowledge in terms of primary principles and by their mental and perceptual deficiencies.  As Robert Hoeldtke, in an historical examination of British medical psychology, points out: “although Locke claimed that the proper function of reason was to associate ideas in a rational fashion, he was more impressed by the peculiar tendency of thoughts to arrange themselves in strange patterns.”  This point is best illustrated by considering the following quotation:


In fine, the defect in naturals seems to proceed from want of quickness, activity, and motion in the intellectual faculties, whereby they are deprived of reason; whereas madmen, on the other side, seem to suffer by the other extreme.  For they do not appear to me to have lost the faculty of reasoning; but having joined together some ideas very wrongly, they mistake them for truths, and they err as men do that argue right from wrong principles.  For by the violence of their imaginations having taken their fancies for realities, they make right deductions from them.


The idiot’s mind suffers from an incapability of discerning, whilst madmen, on the other hand, are deficient in the ability to connect ideas in the right way.  More precisely, the mental faculties of madmen seem to fail to generate, or generate to a greater extent, a comparison of ideas, which equally result in a “faulty mixing of ideas by deranged and violent imagination.”  Locke seems to acknowledge the logical aspects of madness, namely deduction from false premises, in terms of valid reasoning born from a malfunctioning imagination.  Thusly, Locke’s basic view is that “madmen associate ideas incorrectly, whereas idiots were incapable of associating ideas.”  Following Locke, it is safe to conclude that faculties responsible for making logical deductions (from data provided by material sense organs, and thus equipping one’s tabula rasa with ideas) are susceptible to impairment and disability. 


It is also justifiable to assume that Locke regards these capacities as mind’s normal activity.  Following an empiricist view about innate faculties (not ideas and principles), we can consider the following: 


Some of our ideas have a natural correspondence and connexion one with another; it is the office and excellency of our reason to trace these, and hold them together in that union and correspondence which is founded in their peculiar beings.  Beside this, there is another connexion of ideas wholly owing to chance or custom: ideas that in themselves are not all of kin, come to be united in some men’s mind that it is very hard to separate them …


Herein, Locke develops the claim that mental faculties of connection and discerning ideas are to be understood as natural activities, independent of the will of the human mind—they are what we cannot control voluntarily, which is to say, that they are what the mind does normally.  It is best to regard them as “an automatic affair, taking place beyond the control of the active mind.”  Moreover, it is plausible to consider the talk about innateness of mental faculties as a disguised way of talking about their natural or normal functioning.  Thus, Locke writes, that “men, barely by the use of their natural faculties, may attain to all the knowledge they have, without the help of any innate impression, and may arrive at certainty without any such original notions and principles.”  Bearing in mind Locke’s position on innateness, impairment, and natural faculties of mind, we can look, now, into modern philosophical theories of psychopathological conditions.


Modern Theories: Boorse and Wakefield’s Accounts


Although today there is an accepted definition of mental disorder established and propagated by American Psychiatric Association, and included in their influential Diagnostic and Statistical Manual of Mental Disorder (DSM), there has been a burst of philosophical effort to formulate a more adequate and satisfactory account.  Some philosophers and psychiatrists, mainly critics of the definition included in DSM and concept of mental illness in general, in addressing and tackling alleged issues and inadequacy of DSM, tried to incorporate metaphysical, ethical, and Aristotelian philosophical findings in their new theoretical conceptions, thereby creating an array of theories, which eventually resulted in a development of a still growing field of philosophy of psychiatry and philosophical psychopathology. Contrary to anti-psychiatrists and mental disorder skeptics (who are critical towards the mere idea of mental disorder and whose main task is to show that mental illness either does not exist, or, at best, that it is a “historically unstable category”), some psychiatrists, physicians and philosophers have focused on the creation of a more acceptable and precise definition of mental disorders, those that can be accordingly employed in psychiatric practice.  The critics are led by the work of the American-Hungarian psychiatrist Thomas Szasz and the French philosopher and historian Michel Foucault.  Foucault’s main idea is that “contemporary notions of mental illness are rooted in contingent, historical developments,” and, more precisely, that “our thinking of mental disorder … could easily have been different.”  Szasz’s views are far more radical and supported with strong philosophical argumentation, which is apparent in his conclusion that mental disorders do not exist and that we should only regard them as mere myths.  On the other hand, there are those theorists who try to improve the existing definitions and conceptions of mental disorder.  For example, psychiatrist Robert Kendell, in response to Szasz, tries to (re)define mental and physical illnesses in terms of biological disadvantage.  Philosopher Christopher Megone bases his account on an argument that the “concept of mental illness can be satisfactorily clarified if and only if, it is related it to an Aristotelian conception of human nature and human telos.”  British philosopher and psychiatrist Bill Fulford tries to explain illnesses as failures of ordinary doing accompanied with pain.  Each of the above-mentioned accounts played and still play an important role in today’s debates about the existence and nature of mental disorder.  Moreover, with their endeavors to define mental disorder, these theorists have both implicitly and explicitly made a great impact on the definition of physical illness.  It should be noted that some of them have been intensely criticized and disputed; others are still debated today in the field of philosophy of psychiatry.  Besides the above-mentioned accounts, the most prominent position in theorizing about mental disorders is occupied by biological accounts propagated by American philosophers Christopher Boorse and Jerome C. Wakefield.  In what follows, I will briefly outline their basic ideas. 


Even though it is not without critics, the early biological account of mental disorder, proposed by the philosopher Christopher Boorse, represents an attempt to define mental and physical disorders in terms of dysfunctional human bodies and minds.  To achieve this, Boorse based his account on a novel conception of the human body as composed of a number of interrelated parts. To this end, he incorporates in his account a technical notion: “sub-system.”  The liver, heart, skin, eyes, bones, and other parts of body are examples of subsystems. According to philosopher of medicine Sadegh-Zadeh, on a higher level, this definition also involves systems like the cardiovascular system, homeostatic system, immune system, digestive system, nervous system, etc.  In contrast, on a lower level, we can distinguish other parts or constituents like the liver’s right lobe and coronary ligament, the heart’s left atrium, the aorta, nerve cells, etc.  However, it should be noted that a system, while derived from the Greek term σ´υστημα or sistema, which means “standing together,” is not a “mere assemblage … of any objects without any bonds or relationships between them.”  Just the opposite, a system should be regarded as “an entity composed of interrelated parts [consisting of] objects [and the] relationship between these objects.”  Moreover, according to Boorse, every subsystem has a natural function.  As the philosopher Rachel Cooper explains it, “the function of a sub-system is whatever it does that contributes towards achieving the goal of a goal-directed system.”  So, for example, the natural function of the heart is to pump blood through the body.  When this function is executed properly, we are considered healthy.  In contrast, Boorse’s account of disorder is to be understood as a condition in which a sub-system fails to execute its function, and thusly fails to contribute to the higher purpose of the whole organism—in this case, staying alive.  To illustrate this further, consider the coronary artery as a heart’s sub-system, which supplies several sections of the heart with blood.  If the right coronary artery dysfunctions, an interruption of blood supply occurs and leads to myocardial infarction, in which a higher sub-system dysfunctions and leads to a failure of a goal-directed system.  In other words, according to Boorse, a heart attack is a pathological condition because it represents the heart’s failure to execute its function of pumping blood.


A similar account of disorder is presented by the American philosopher Jerome Wakefield.  Wakefield follows Boorse’s conception of a disorder except that he claims that mental disorder must also be considered as a harmful dysfunction, wherein harmful denotes a value notion and refers to social norms.  Wakefield writes:


Suppose that one function of [the] learning mechanism is to associate the response of fear with danger. …  Sometimes a severe trauma or other unusual sequence of stimuli causes the formation of an enduringly exaggerated sense of danger that causes substantial harm to a person.  Such a disposition constitutes a disorder, because not only is there a dysfunction … but there is also a harm (the exaggerated fear is painful of disabling).


Similarly to Boorse, Wakefield keeps his definition within biological theory and remains committed to the notion of a failure of biological function.  However, he importantly adds to his account the notion of values.  Not only does a disorder represent a dysfunction of a certain mechanism in a human organism, it also involves undesirable, painful, harmful, dangerous, and ruinous aspects and consequences.  In other words, mental disorders depend on a dysfunctional condition that is negatively valued by society.  This part of his account makes use of medical praxicology in certain cases.  It is also important to mention that Wakefield argues that the DSM definition is based on the idea that a condition is a disorder if and only if it is a harmful dysfunction.  


Here, two questions arise.  First, how can we connect the above-mentioned examples to Locke’s idiots and madmen?  And, second, what are the reasons for the working conclusion that Locke anticipated modern theories?


Similarities between Locke and Modern Theories


We said that, according to Locke, idiots suffer from an incapability to discern and reason, whilst madmen, on the other hand, are primarily deficient in the ability to connect ideas in the right way.  Thus, I claim that such an observation suggests a rather strong resemblance, not only between Locke’s conception of madness and modern psychiatric conception of delusion, but also between Locke and modern accounts of mental disorder in general.  Conceptual analysis allows certain paraphrases of Locke’s ideas and definitions thusly providing satisfying interpretation of his philosophy of mind that incorporates the empiricist postulation of innate mental capacities.  Let us consider one such satisfying clarification of Locke’s position that brings out these resemblances.  Locke, as we said, depicts the human mind as composed of a number of mental faculties whose functioning results in reasoning, logical deduction, imagination, understanding, the comparison of ideas, and so forth; it is a feature which induces the “nobleness” of the human mind and “sets man above other sensible beings.”  These are natural features of the human mind that enable our specific functions in everyday cooperative, independent, and passive activities.  This claim can be easily paraphrased into a definition of the mind as “an arrangement of circumstances that makes things happen in a certain way.”  This paraphrase is a representative example of a list of conditions of what makes something a system in the above-mentioned way.  Mental capacities are organized in a certain way.  In addition, these mental capacities are interrelated in a way that results in specific manifestations: reasoning, normal mental functioning, etc. 


Here, we have an easily perceived one-to-one correspondence between Locke and Boorse’s theories of mental disorder.  In other words, the former’s term “mind” and the latter’s term “system” are co-referential—they refer to the same thing.  Cooper captures it succinctly in her remark that “organs, such as the nervous system and mental modules (if there are any) will all count as Boorsean sub-system.”  Mind, as a system, in order to function, is composed of numerous sub-systems, which, on the other hand, function in their own right and strive towards the goal of the whole system.  According to Boorse, sub-systems are susceptible to dysfunction, which leads to the failure to fulfill the goal of the goal-directed system.  Locke has a similar conclusion—he writes that:


Those who cannot distinguish, compare, and abstract, would hardly be able to understand … or reason, to any tolerable degree; but only a little and imperfectly. …  And indeed any of the fore-mentioned faculties, if wanting or out of order, produce suitable defects in men’s understanding and knowledge.


We have, thus, another correlation: namely, between disability or defect of Locke’s mental faculties and Boorse’s goal dysfunction of the goal-directed sub-systems.  Another striking similarity refers to the mind as a goal-directed system.  As noted above, the mental faculties of the mentally stable enable their specific functions in everyday cooperative, independent, and passive activities.  These activities can be understood as the goal of the mind as a system.  Consider, for example, this representative passage: 


This wrong connexion in our mind of ideas, in themselves loose and independent on of another, has such and influence, and is of so great force, to set us awry in our actions, as well as moral and natural, passions, reasonings, and notions themselves, that perhaps there is not any one thing that deserves more to be looked after.


And again:


Thus you shall find a distracted man, fancying himself a king, with a right inference, require suitable attendance, respect, and obedience; others, who have thought themselves made of glass, have used the caution necessary to preserve such brittle bodies.


This is due to the dysfunction of mental capacities of reasoning, or as Locke puts it “either by any sudden very strong impression, or long fixing his fancy … incoherent ideas have been cemented together so powerfully as to remain united.”  These quotations provide us with important concepts that ought to be extracted and then must be clarified:


1) The wrong connection of ideas, 

2) Which can set us awry in our actions,

3) Which can set us awry in our moral actions, 

4) And which can set us awry in our natural actions, passions, reasoning and notions themselves.


Here, again, an analogy between Locke’s theory and Boorse’s account is easily perceived.  The key concept (1) “The wrong connection of ideas,” a mental ability that we can consider as a sub-system of the mind, is Locke’s connection of ideas—a sub-system that, in the case of idiots and madmen, quite clearly dysfunctions and fails to contribute to a goal-directed system.  More precisely, idiots’ minds are dysfunctional in the sense of their lacking of mental capacities; madmen’s minds, on the other hand, are dysfunctional in the sense of the wrong connection of ideas. 


Claims (2), (3), and (4) point to Locke’s assumptions about potentially dangerous consequences of dysfunctional acts.  The former key claim (1) clearly gives us an insight into these disabling consequences, namely, that the dysfunction of mental faculties can render us inoperative in everyday activity.  In a nutshell, the mental dysfunction of the incorrect connection of ideas may often influence the moral and social conduct of a subject.  The madman, according to Locke, may imagine that he is made of glass, which was presumably a common mental disorder of Locke’s time.  In accordance with his state, the subject exhibits inappropriate social behaviors, which may lead to a number of undesired and harmful consequences.  Locke explicitly relies on a harm of madness.  Thus, he regards man’s healing from madness “as the greatest obligation he could have received.”   And, here, we have a similarity between Locke and Wakefield’s account of mental disorder as a harmful dysfunction.


However, one may ask whether or not the similarities are outweighed by the differences. Some of the differences may be based on the ways by which views of the human mind, systems, and mechanisms have evolved since Locke’s day.  For example, the emphasis on logical reasoning has since greatly diminished, with more emphasis turned to the non-logical aspects of thought; further, self-consciousness, linguistic culture, emotions, embodiment, and other aspects barely approached and addressed in Locke’s Essay are today widely considered.  In addition, rather than limiting the notion of madness to correct deductions from false premises, modern theorists assume a much more complex interplay of different factors, all of which can malfunction in very different ways.  Such theorists may regard Locke’s account as peripheral to any general account of mental disorder.  Nevertheless, I am inclined to think that any lack of knowledge as to modern philosophical and metaphysical theories simply does not result in a difference in attitude towards certain philosophical problems—an attitude that Locke, as I have shown, clearly took.  And, as I have also shown, there is a clear existence of co-referential terms in both Locke’s and modern accounts of mental disorder.  Finally, even if it may be, concerning his clarification of madness, that Locke is on very edge of the psychiatric domain, this critique cannot be applied to a philosophy of psychiatry and philosophical psychopathology, which, eventually was an aim of this paper.




Although the definition of mental disorder based on harmful dysfunction is considered to be a philosophical and theoretical construct of modern philosophy of psychiatry, it seems obvious that Locke provided a rough sketch of this account.  This is an interesting observation considering more than three hundred years of difference between advocates of these positions.  This gives us a strong reason to conclude that Locke anticipated modern theories.  This also shows that the claim proposed by James and Morley should not be regarded as wrong, but rather as incomplete.  Making one step ahead, I tried to show that Locke’s conception of madness anticipates two modern philosophical theories of mental disorder.  Thus, by comparing Locke’s theory with Boorse’s biological account, I have suggested that psychopathological states, as explained by Locke, may be clarified as dysfunctions of an organism’s sub-system.  Also, I have emphasized the similarities between his account and Wakefield’s theory of disorder as harmful dysfunction.  I have explained this by pointing out that the dysfunction of mental capacities may have dangerous consequences for the individual and his or her immediate surroundings.  Locke’s Essay, therefore, proves to be an undoubtedly important resource for the historical and philosophical examination of some early thoughts on philosophical psychopathology.  Despite the origin of philosophical psychopathology generally considered to be Karl Jaspers’ influential work General Psychopathology (written in 1910 and published in 1913), it is obvious that important conceptions were conceived significantly earlier—namely with John Locke, thusly making him a precursor of modern ideas of philosophy of psychiatry and philosophical psychopathology, a prominent figure of theoretical, and no less significantly, historical importance.



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