Absurdism

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This article is about the philosophical theory. For other uses, see absurdist (disambiguation).

Sisyphus, the symbol of the absurdity of existence, painting by Franz Stuck (1920)

Absurdism is the philosophical theory that the universe is irrational and meaningless. It states that trying to find meaning leads people into conflict with a seemingly meaningless world. This conflict can be between rational humanity and an irrational universe, between intention and outcome, or between subjective assessment and objective worth, but the precise definition of the term is disputed. Absurdism claims that, due to one or more of these conflicts, existence as a whole is absurd. It differs in this regard from the less global thesis that some particular situations, persons, or phases in life are absurd.

Various components of the absurd are discussed in the academic literature, and different theorists frequently concentrate their definition and research on different components. On the practical level, the conflict underlying the absurd is characterized by the individual's struggle to find meaning in a meaningless world. The theoretical component, on the other hand, emphasizes more the epistemic inability of reason to penetrate and understand reality. Traditionally, the conflict is characterized as a collision between an internal component of human nature, and an external component of the universe. However, some later theorists have suggested that both components may be internal: the capacity to see through the arbitrariness of any ultimate purpose, on the one hand, and the incapacity to stop caring about such purposes, on the other hand. Certain accounts also involve a metacognitive component by holding that an awareness of the conflict is necessary for the absurd to arise.

Some arguments in favor of absurdism focus on the human insignificance in the universe, on the role of death, or on the implausibility or irrationality of positing an ultimate purpose. Objections to absurdism often contend that life is in fact meaningful or point out certain problematic consequences or inconsistencies of absurdism. Defenders of absurdism often complain that it does not receive the attention of professional philosophers that it merits in virtue of the topic's importance and its potential psychological impact on the affected individuals in the form of existential crises. Various possible responses to deal with absurdism and its impact have been suggested. The three responses discussed in the traditional absurdist literature are suicide, religious belief in a higher purpose, and rebellion against the absurd. Of these, rebellion is usually presented as the recommended response since, unlike the other two responses, it does not escape the absurd and instead recognizes it for what it is. Later theorists have suggested additional responses, like using irony to take life less seriously or remaining ignorant of the responsible conflict. Some absurdists argue that whether and how one responds is insignificant. This is based on the idea that if nothing really matters, then the human response toward this fact does not matter either.

The term "absurdism" is most closely associated with the philosophy of Albert Camus. However, important precursors and discussions of the absurd are also found in the works of Søren Kierkegaard. Absurdism is intimately related to various other concepts and theories. Its basic outlook is inspired by existentialist philosophy. However, existentialism includes additional theoretical commitments and often takes a more optimistic attitude toward the possibility of finding or creating meaning in one's life. Absurdism and nihilism share the belief that life is meaningless, but absurdists do not treat this as an isolated fact and are instead interested in the conflict between the human desire for meaning and the world's lack thereof. Being confronted with this conflict may trigger an existential crisis, in which unpleasant experiences like anxiety or depression may push the affected to find a response for dealing with the conflict. Recognizing the absence of objective meaning, however, does not preclude the conscious thinker from finding subjective meaning.

Definition

Absurdism is the philosophical thesis that life, or the world in general, is absurd. There is wide agreement that the term "absurd" implies a lack of meaning or purpose, but there is also significant dispute concerning its exact definition and various versions have been suggested. The choice of one's definition has important implications for whether the thesis of absurdism is correct and for the arguments cited for and against it: it may be true on one definition and false on another.

In a general sense, the absurd is that which lacks a sense, often because it involves some form of contradiction. The absurd is paradoxical in the sense that it cannot be grasped by reason. But in the context of absurdism, the term is usually used in a more specific sense. According to most definitions, it involves a conflict, discrepancy, or collision between two things. Opinions differ on what these two things are. For example, it is traditionally identified as the confrontation of rational man with an irrational world or as the attempt to grasp something based on reasons even though it is beyond the limits of rationality. Similar definitions see the discrepancy between intention and outcome, between aspiration and reality, or between subjective assessment and objective worth as the source of absurdity. Other definitions locate both conflicting sides within man: the ability to apprehend the arbitrariness of final ends and the inability to let go of commitments to them. In regard to the conflict, absurdism differs from nihilism since it is not just the thesis that nothing matters. Instead, it includes the component that things seem to matter to us nonetheless and that this impression cannot be shaken off. This difference is expressed in the relational aspect of the absurd in that it constitutes a conflict between two sides.

Various components of the absurd have been suggested and different researchers often focus their definition and inquiry on one of these components. Some accounts emphasize the practical components concerned with the individual seeking meaning while others stress the theoretical components about being unable to know the world or to rationally grasp it. A different disagreement concerns whether the conflict exists only internal to the individual or is between the individual's expectations and the external world. Some theorists also include the metacognitive component that the absurd entails that the individual is aware of this conflict.

An important aspect of absurdism is that the absurd is not limited to particular situations but encompasses life as a whole. There is a general agreement that people are often confronted with absurd situations in everyday life. They often arise when there is a serious mismatch between one's intentions and reality. For example, a person struggling to break down a heavy front door is absurd if the house they are trying to break into lacks a back wall and could easily be entered on this route. But the philosophical thesis of absurdism is much more wide-reaching since it is not restricted to individual situations, persons, or phases in life. Instead, it asserts that life, or the world as a whole, is absurd. The claim that the absurd has such a global extension is controversial, in contrast to the weaker claim that some situations are absurd.

The perspective of absurdism usually comes into view when the agent takes a step back from their individual everyday engagements with the world to assess their importance from a bigger context. Such an assessment can result in the insight that the day-to-day engagements matter a lot to us despite the fact that they lack real meaning when evaluated from a wider perspective. This assessment reveals the conflict between the significance seen from the internal perspective and the arbitrariness revealed through the external perspective. The absurd becomes a problem since there is a strong desire for meaning and purpose even though they seem to be absent. In this sense, the conflict responsible for the absurd often either constitutes or is accompanied by an existential crisis.

Components

Practical and theoretical

An important component of the absurd on the practical level concerns the seriousness people bring toward life. This seriousness is reflected in many different attitudes and areas, for example, concerning fame, pleasure, justice, knowledge, or survival, both in regard to ourselves as well as in regard to others. But there seems to be a discrepancy between how seriously we take our lives and the lives of others on the one hand, and how arbitrary they and the world at large seem to be on the other hand. This can be understood in terms of importance and caring: it is absurd that people continue to care about these matters even though they seem to lack importance on an objective level. The collision between these two sides can be defined as the absurd. This is perhaps best exemplified when the agent is seriously engaged in choosing between arbitrary options, none of which truly matters.

Some theorists characterize the ethical sides of absurdism and nihilism in the same way as the view that it does not matter how we act or that "everything is permitted." On this view, an important aspect of the absurd is that whatever higher end or purpose we choose to pursue, it can also be put into doubt since, in the last step, it always lacks a higher-order justification. But usually, a distinction between absurdism and nihilism is made since absurdism involves the additional component that there is a conflict between man's desire for meaning and the absence of meaning.

On a more theoretical view, absurdism is the belief that the world is, at its core, indifferent and impenetrable toward human attempts to uncover its deeper reason or that it cannot be known. According to this theoretical component, it involves the epistemological problem of the human limitations of knowing the world. This includes the thesis that the world is in critical ways ungraspable to humans, both in relation to what to believe and how to act. This is reflected in the chaos and irrationality of the universe, which acts according to its own laws in a manner indifferent to human concerns and aspirations. It is closely related to the idea that the world remains silent when we ask why things are the way they are. This silence arises from the impression that, on the most fundamental level, all things exist without a reason: they are simply there. An important aspect of these limitations to knowing the world is that they are essential to human cognition, i.e. they are not due to following false principles or accidental weaknesses but are inherent in the human cognitive faculties themselves.

Some theorists also link this problem to the circularity of human reason, which is very skilled at producing chains of justification linking one thing to another while trying and failing to do the same for the chain of justification as a whole when taking a reflective step backward. This implies that human reason is not just too limited to grasp life as a whole, but that, if one seriously tried to do so anyway, its ungrounded circularity might collapse and lead to madness.

Internal and external

An important disagreement within the academic literature about the nature of absurdism and the absurd focuses specifically on whether the components responsible for the conflict are internal or external. According to the traditional position, the absurd has both internal and external components: it is due to the discrepancy between man's internal desire to lead a meaningful life and the external meaninglessness of the world. In this view, humans have, among their desires, some transcendent aspirations that seek a higher form of meaning in life. The absurd arises since these aspirations are ignored by the world, which is indifferent to our "need for validation of the importance of our concerns." This implies that the absurd "is not in man ... nor in the world, but in their presence together." This position has been rejected by some later theorists, who hold that the absurd is purely internal because it "derives not from a collision between our expectations and the world, but from a collision within ourselves".

The distinction is important since, on the latter view, the absurd is built into human nature and would prevail no matter what the world was like. So, it is not just that absurdism is true in the actual world. Instead, any possible world, even one that was designed by a divine god and guided by them according to their higher purpose, would still be equally absurd to man. In this sense, absurdity is the product of the power of our consciousness to take a step back from whatever it is considering and reflect on the reason of its object. When this process is applied to the world as a whole, including God, it is bound to fail its search for a reason or an explanation, no matter what the world is like. In this sense, absurdity arises from the conflict between features of ourselves: "our capacity to recognize the arbitrariness of our ultimate concerns and our simultaneous incapacity to relinquish our commitment to them". This view has the side effect that the absurd depends on the fact that the affected person recognizes it. For example, people who fail to apprehend the arbitrariness or the conflict would not be affected.

Metacognitive

According to some researchers, a central aspect of the absurd is that the agent is aware of the existence of the corresponding conflict. This means that the person is conscious both of the seriousness they invest and of how it seems misplaced in an arbitrary world. It also implies that other entities that lack this form of consciousness, like non-organic matter or lower life forms, are not absurd and are not faced with this particular problem. Some theorists also emphasize that the conflict remains despite the individual's awareness of it, i.e. that the individual continues to care about their everyday concerns despite their impression that, on the large scale, these concerns are meaningless. Defenders of the metacognitive component have argued that it manages to explain why absurdity is primarily ascribed to human aspirations but not to lower animals: because they lack this metacognitive awareness. However, other researchers reject the metacognitive requirement based on the fact that it would severely limit the scope of the absurd to only those possibly few individuals who clearly recognize the contradiction while sparing the rest. Thus, opponents have argued that not recognizing the conflict is just as absurd as consciously living through it.

Arguments

For

Thomas Nagel examined the nature of the absurd, considering arguments and responses to it.

Various popular arguments are often cited in favor of absurdism. Some focus on the future by pointing out that nothing we do today will matter in a million years. A similar line of argument points to the fact that our lives are insignificant because of how small they are in relation to the universe as a whole, both concerning their spatial and their temporal dimensions. The thesis of absurdism is also sometimes based on the problem of death, i.e. that there is no final end for us to pursue since we are all going to die. In this sense, death is said to destroy all our hard-earned achievements like career, wealth, or knowledge. This argument is mitigated to some extent by the fact that we may have positive or negative effects on the lives of other people as well. But this does not fully solve the issue since the same problem, i.e. the lack of an ultimate end, applies to their lives as well. Thomas Nagel has objected to these lines of argument based on the claim that they are circular: they assume rather than establish that life is absurd. For example, the claim that our actions today will not matter in a million years does not directly imply that they do not matter today. And similarly, the fact that a process does not reach a meaningful ultimate goal does not entail that the process as a whole is worthless since some parts of the process may contain their justification without depending on a justification external to them.

Another argument proceeds indirectly by pointing out how various great thinkers have obvious irrational elements in their systems of thought. These purported mistakes of reason are then taken as signs of absurdism that were meant to hide or avoid it. From this perspective, the tendency to posit the existence of a benevolent God may be seen as a form of defense mechanism or wishful thinking to avoid an unsettling and inconvenient truth. This is closely related to the idea that humans have an inborn desire for meaning and purpose, which is dwarfed by a meaningless and indifferent universe. For example, René Descartes aims to build a philosophical system based on the absolute certainty of the "I think, therefore I am" just to introduce without a proper justification the existence of a benevolent and non-deceiving God in a later step in order to ensure that we can know about the external world. A similar problematic step is taken by John Locke, who accepts the existence of a God beyond sensory experience, despite his strict empiricism, which demands that all knowledge be based on sensory experience.

Other theorists argue in favor of absurdism based on the claim that meaning is relational. In this sense, for something to be meaningful, it has to stand in relation to something else that is meaningful. For example, a word is meaningful because of its relation to a language or someone's life could be meaningful because this person dedicates their efforts to a higher meaningful project, like serving God or fighting poverty. An important consequence of this characterization of meaning is that it threatens to lead to an infinite regress: at each step, something is meaningful because something else is meaningful, which in its turn has meaning only because it is related to yet another meaningful thing, and so on. This infinite chain and the corresponding absurdity could be avoided if some things had intrinsic or ultimate meaning, i.e. if their meaning did not depend on the meaning of something else. For example, if things on the large scale, like God or fighting poverty, had meaning, then our everyday engagements could be meaningful by standing in the right relation to them. However, if these wider contexts themselves lack meaning then they are unable to act as sources of meaning for other things. This would lead to the absurd when understood as the conflict between the impression that our everyday engagements are meaningful even though they lack meaning because they do not stand in a relation to something else that is meaningful.

Another argument for absurdism is based on the attempt of assessing standards of what matters and why it matters. It has been argued that the only way to answer such a question is in reference to these standards themselves. This means that, in the end, it depends only on us, that "what seems to us important or serious or valuable would not seem so if we were differently constituted". The circularity and groundlessness of these standards themselves are then used to argue for absurdism.

Against

The most common criticism of absurdism is to argue that life in fact has meaning. Supernaturalist arguments to this effect are based on the claim that God exists and acts as the source of meaning. Naturalist arguments, on the other hand, contend that various sources of meaning can be found in the natural world without recourse to a supernatural realm. Some of them hold that meaning is subjective. On this view, whether a given thing is meaningful varies from person to person based on their subjective attitude toward this thing. Others find meaning in external values, for example, in morality, knowledge, or beauty. All these different positions have in common that they affirm the existence of meaning, in contrast to absurdism.

Another criticism of absurdism focuses on its negative attitude toward moral values. In the absurdist literature, the moral dimension is sometimes outright denied, for example, by holding that value judgments are to be discarded or that the rejection of God implies the rejection of moral values. On this view, absurdism brings with it a highly controversial form of moral nihilism. This means that there is a lack, not just of a higher purpose in life, but also of moral values. These two sides can be linked by the idea that without a higher purpose, nothing is worth pursuing that could give one's life meaning. This worthlessness seems to apply to morally relevant actions equally as to other issues. In this sense, "[b]elief in the meaning of life always implies a scale of values" while "[b]elief in the absurd ... teaches the contrary". Various objections to such a position have been presented, for example, that it violates common sense or that it leads to numerous radical consequences, like that no one is ever guilty of any blameworthy behavior or that there are no ethical rules.

But this negative attitude toward moral values is not always consistently maintained by absurdists and some of the suggested responses on how to deal with the absurd seem to explicitly defend the existence of moral values. Due to this ambiguity, other critics of absurdism have objected to it based on its inconsistency. The moral values defended by absurdists often overlap with the ethical outlook of existentialism and include traits like sincerity, authenticity, and courage as virtues. In this sense, absurdists often argue that it matters how the agent faces the absurdity of their situation and that the response should exemplify these virtues. This aspect is particularly prominent in the idea that the agent should rebel against the absurd and live their life authentically as a form of passionate revolt.

Some see the latter position as inconsistent with the idea that there is no meaning in life: if nothing matters then it should also not matter how we respond to this fact. Defenders of absurdism have tried to resist this line of argument by contending that, in contrast to other responses, it remains true to the basic insight of absurdism and the "logic of the absurd" by acknowledging the existence of the absurd instead of denying it. But this defense is not always accepted. One of its shortcomings seems to be that it commits the is-ought fallacy: absurdism presents itself as a descriptive claim about the existence and nature of the absurd but then goes on to posit various normative claims. Another defense of absurdism consists in weakening the claims about how one should respond to the absurd and which virtues such a response should exemplify. On this view, absurdism may be understood as a form of self-help that merely provides prudential advice. Such prudential advice may be helpful to certain people without pretending to have the status of universally valid moral values or categorical normative judgments. So the value of the prudential advice may merely be relative to the interests of some people but not valuable in a more general sense. This way, absurdists have tried to resolve the apparent inconsistency in their position.

Examples

According to absurdism, life in general is absurd: the absurd is not just limited to a few specific cases. Nonetheless, some cases are more paradigmatic examples than others. The Myth of Sisyphus is often treated as a key example of the absurd. In it, Zeus punishes King Sisyphus by compelling him to roll a massive boulder up a hill. Whenever the boulder reaches the top, it rolls down again, thereby forcing Sisyphus to repeat the same task all over again throughout eternity. This story may be seen as an absurdist parable for the hopelessness and futility of human life in general: just like Sisyphus, humans in general are condemned to toil day in and day out in the attempt to fulfill pointless tasks, which will be replaced by new pointless tasks once they are completed. It has been argued that a central aspect of Sisyphus' situation is not just the futility of his labor but also his awareness of the futility.

Franz Kafka's book The Trial (German: Der Prozess) examines the absurdity of life through the lens of an impenetrable judicial system.

Another example of the absurdist aspect of the human condition is given in Franz Kafka's The Trial. In it, the protagonist Josef K. is arrested and prosecuted by an inaccessible authority even though he is convinced that he has done nothing wrong. Throughout the story, he desperately tries to discover what crimes he is accused of and how to defend himself. But in the end, he lets go of his futile attempts and submits to his execution without ever finding out what he was accused of. The absurd nature of the world is exemplified by the mysterious and impenetrable functioning of the judicial system, which seems indifferent to Josef K. and resists all of his attempts of making sense of it.

Importance

Philosophers of absurdism often complain that the topic of the absurd does not receive the attention of professional philosophers it merits, especially when compared to other perennial philosophical areas of inquiry. It has been argued, for example, that this can be seen in the tendency of various philosophers throughout the ages to include the epistemically dubitable existence of God in their philosophical systems as a source of ultimate explanation of the mysteries of existence. In that regard, this tendency may be seen as a form of defense mechanism or wishful thinking constituting a side-effect of the unacknowledged and ignored importance of the absurd. While some discussions of absurdism happen explicitly in the philosophical literature, it is often presented in a less explicit manner in the form of novels or plays. These presentations usually happen by telling stories that exemplify some of the key aspects of absurdism even though they may not explicitly discuss the topic.

It has been argued that acknowledging the existence of the absurd has important consequences for epistemology, especially in relation to philosophy but also when applied more widely to other fields. The reason for this is that acknowledging the absurd includes becoming aware of human cognitive limitations and may lead to a form of epistemic humbleness.

The impression that life is absurd may in some cases have serious psychological consequences like triggering an existential crisis. In this regard, an awareness both of absurdism itself and the possible responses to it can be central to avoiding or resolving such consequences.

Possible responses

... in spite of or in defiance of the whole of existence he wills to be himself with it, to take it along, almost defying his torment. For to hope in the possibility of help, not to speak of help by virtue of the absurd, that for God all things are possible—no, that he will not do. And as for seeking help from any other—no, that he will not do for all the world; rather than seek help he would prefer to be himself—with all the tortures of hell, if so it must be.

— Søren Kierkegaard, The Sickness Unto Death

Most researchers argue that the basic conflict posed by the absurd cannot be truly resolved. This means that any attempt to do so is bound to fail even though their protagonists may not be aware of their failure. On this view, there are still several possible responses, some better than others, but none able to solve the fundamental conflict. Traditional absurdism, as exemplified by Albert Camus, holds that there are three possible responses to absurdism: suicide, religious belief, or revolting against the absurd. Later researchers have suggested more ways of responding to absurdism.

A very blunt and simple response, though quite radical, is to commit suicide. According to Camus, for example, the problem of suicide is the only "really serious philosophical problem". It consists in seeking an answer to the question "Should I kill myself?". This response is motivated by the insight that, no matter how hard the agent tries, they may never reach their goal of leading a meaningful life, which can then justify the rejection of continuing to live at all. Most researchers acknowledge that this is one form of response to the absurd but reject it due to its radical and irreversible nature and argue instead for a different approach.

One such alternative response to the apparent absurdity of life is to assume that there is some higher ultimate purpose in which the individual may participate, like service to society, progress of history, or God's glory. While the individual may only play a small part in the realization of this overarching purpose, it may still act as a source of meaning. This way, the individual may find meaning and thereby escape the absurd. One serious issue with this approach is that the problem of absurdity applies to this alleged higher purpose as well. So just like the aims of a single individual life can be put into doubt, this applies equally to a larger purpose shared by many. And if this purpose is itself absurd, it fails to act as a source of meaning for the individual participating in it. Camus identifies this response as a form of suicide as well, pertaining not to the physical but to the philosophical level. It is a philosophical suicide in the sense that the individual just assumes that the chosen higher purpose is meaningful and thereby fails to reflect on its absurdity.

Traditional absurdists usually reject both physical and philosophical suicide as the recommended response to the absurd, usually with the argument that both these responses constitute some form of escape that fails to face the absurd for what it is. Despite the gravity and inevitability of the absurd, they recommend that we should face it directly, i.e. not escape from it by retreating into the illusion of false hope or by ending one's life. In this sense, accepting the reality of the absurd means rejecting any hopes for a happy afterlife free of those contradictions. Instead, the individual should acknowledge the absurd and engage in a rebellion against it. Such a revolt usually exemplifies certain virtues closely related to existentialism, like the affirmation of one's freedom in the face of adversity as well as accepting responsibility and defining one's own essence. An important aspect of this lifestyle is that life is lived passionately and intensely by inviting and seeking new experiences. Such a lifestyle might be exemplified by an actor, a conqueror, or a seduction artist who is constantly on the lookout for new roles, conquests, or attractive people despite their awareness of the absurdity of these enterprises. Another aspect lies in creativity, i.e. that the agent sees themselves as and acts as the creator of their own works and paths in life. This constitutes a form of rebellion in the sense that the agent remains aware of the absurdity of the world and their part in it but keeps on opposing it instead of resigning and admitting defeat. But this response does not solve the problem of the absurd at its core: even a life dedicated to the rebellion against the absurd is itself still absurd. Defenders of the rebellious response to absurdism have pointed out that, despite its possible shortcomings, it has one important advantage over many of its alternatives: it manages to accept the absurd for what it is without denying it by rejecting that it exists or by stopping one's own existence. Some even hold that it is the only philosophically coherent response to the absurd.

While these three responses are the most prominent ones in the traditional absurdist literature, various other responses have also been suggested. Instead of rebellion, for example, absurdism may also lead to a form of irony. This irony is not sufficient to escape the absurdity of life altogether, but it may mitigate it to some extent by distancing oneself to some degree from the seriousness of life. According to Thomas Nagel, there may be, at least theoretically, two responses to actually resolving the problem of the absurd. This is based on the idea that the absurd arises from the consciousness of a conflict between two aspects of human life: that humans care about various things and that the world seems arbitrary and does not merit this concern. The absurd would not arise if either of the conflicting elements would cease to exist, i.e. if the individual would stop caring about things, as some Eastern religions seem to suggest, or if one could find something that possesses a non-arbitrary meaning that merits the concern. For theorists who give importance to the consciousness of this conflict for the absurd, a further option presents itself: to remain ignorant of it to the extent that this is possible.

Other theorists hold that a proper response to the absurd may neither be possible nor necessary, that it just remains one of the basic aspects of life no matter how it is confronted. This lack of response may be justified through the thesis of absurdism itself: if nothing really matters on the grand scale, then this applies equally to human responses toward this fact. From this perspective, the passionate rebellion against an apparently trivial or unimportant state of affairs seems less like a heroic quest and more like a fool's errand. Jeffrey Gordon has objected to this criticism based on the claim that there is a difference between absurdity and lack of importance. So even if life as a whole is absurd, some facts about life may still be more important than others and the fact that life as a whole is absurd would be a good candidate for the more important facts.

History

Certain precursors to absurdism are found in Ecclesiastes, a book of the Bible, and in the works of William Shakespeare. Absurdism has its origins in the work of the 19th-century Danish philosopher Søren Kierkegaard, who chose to confront the crisis that humans face with the Absurd by developing his own existentialist philosophy. Absurdism as a belief system was born of the European existentialist movement that ensued, specifically when Camus rejected certain aspects of that philosophical line of thought and published his essay The Myth of Sisyphus. The aftermath of World War II provided the social environment that stimulated absurdist views and allowed for their popular development, especially in the devastated country of France. Foucault viewed Shakespearean theater as a precursor of absurdism.

Immanuel Kant

An idea very close to the concept of the absurd is due to Immanuel Kant, who distinguishes between phenomena and noumena. This distinction refers to the gap between how things appear to us and what they are like in themselves. For example, according to Kant, space and times are dimensions belonging to the realm of phenomena since this is how sensory impressions are organized by the mind, but may not be found on the level of noumena. The concept of the absurd corresponds to the thesis that there is such a gap and human limitations may limit the mind from ever truly grasping reality, i.e. that reality in this sense remains absurd to the mind.

Søren Kierkegaard

Main article: Philosophy of Søren Kierkegaard

Kierkegaard designed the relationship framework based (in part) on how a person reacts to despair. Absurdist philosophy fits into the 'despair of defiance' rubric.

A century before Camus, the 19th-century Danish philosopher Søren Kierkegaard wrote extensively about the absurdity of the world. In his journals, Kierkegaard writes about the absurd:

What is the Absurd? It is, as may quite easily be seen, that I, a rational being, must act in a case where my reason, my powers of reflection, tell me: you can just as well do the one thing as the other, that is to say where my reason and reflection say: you cannot act and yet here is where I have to act... The Absurd, or to act by virtue of the absurd, is to act upon faith ... I must act, but reflection has closed the road so I take one of the possibilities and say: This is what I do, I cannot do otherwise because I am brought to a standstill by my powers of reflection.

— Kierkegaard, Søren, Journals, 1849

Here is another example of the Absurd from his writings:

What, then, is the absurd? The absurd is that the eternal truth has come into existence in time, that God has come into existence, has been born, has grown up. etc., has come into existence exactly as an individual human being, indistinguishable from any other human being, in as much as all immediate recognizability is pre-Socratic paganism and from the Jewish point of view is idolatry.

— Kierkegaard, Concluding Unscientific Postscript, 1846, Hong 1992, p. 210

How can this absurdity be held or believed? Kierkegaard says:

I gladly undertake, by way of brief repetition, to emphasize what other pseudonyms have emphasized. The absurd is not the absurd or absurdities without any distinction (wherefore Johannes de Silentio: "How many of our age understand what the absurd is?"). The absurd is a category, and the most developed thought is required to define the Christian absurd accurately and with conceptual correctness. The absurd is a category, the negative criterion, of the divine or of the relationship to the divine. When the believer has faith, the absurd is not the absurd—faith transforms it, but in every weak moment it is again more or less absurd to him. The passion of faith is the only thing which masters the absurd—if not, then faith is not faith in the strictest sense, but a kind of knowledge. The absurd terminates negatively before the sphere of faith, which is a sphere by itself. To a third person the believer relates himself by virtue of the absurd; so must a third person judge, for a third person does not have the passion of faith. Johannes de Silentio has never claimed to be a believer; just the opposite, he has explained that he is not a believer—in order to illuminate faith negatively.

— Journals of Søren Kierkegaard X6B 79

Kierkegaard provides an example in Fear and Trembling (1843), which was published under the pseudonym Johannes de Silentio. In the story of Abraham in the Book of Genesis, Abraham is told by God to kill his son Isaac. Just as Abraham is about to kill Isaac, an angel stops Abraham from doing so. Kierkegaard believes that through virtue of the absurd, Abraham, defying all reason and ethical duties ("you cannot act"), got back his son and reaffirmed his faith ("where I have to act").

Another instance of absurdist themes in Kierkegaard's work appears in The Sickness Unto Death, which Kierkegaard signed with pseudonym Anti-Climacus. Exploring the forms of despair, Kierkegaard examines the type of despair known as defiance. In the opening quotation reproduced at the beginning of the article, Kierkegaard describes how such a man would endure such a defiance and identifies the three major traits of the Absurd Man, later discussed by Albert Camus: a rejection of escaping existence (suicide), a rejection of help from a higher power and acceptance of his absurd (and despairing) condition.

According to Kierkegaard in his autobiography The Point of View of My Work as an Author, most of his pseudonymous writings are not necessarily reflective of his own opinions. Nevertheless, his work anticipated many absurdist themes and provided its theoretical background.

Albert Camus

Albert Camus in 1945

The philosophy of Albert Camus, or more precisely the "camusian absurd" (French : l'absurde camusien), refers with absurdism to the work and philosophical thought of the French writer Albert Camus. This philosophy is influenced by the author's political, libertarian, social and ecological ideas; and is inspired by previous philosophical trends, such as Greek philosophy, nihilism, the Nietzschean thought or existentialism. It revolves around three major cycles: "the absurd (l'absurde)", "the revolt (la révolte)" and "love (l'amour)". Each cycle is linked to a Greek myth (Sisyphus, Prometheus, Nemesis) and explores specific themes and objects; the common thread remaining the solitude and despair of the human, constantly driven by the tireless search for the meaning of the world and of life.

I had a precise plan when I started my work: I wanted to first express negation. In three forms. Romanesque: it was The Stranger. Drama: Caligula and The Misunderstanding. Ideological: The Myth of Sisyphus. I wouldn't have been able to talk about it if I hadn't experienced it; I have no imagination. But for me it was, if you like, the methodical doubt of Descartes. I knew that we cannot live in negation and I announced it in the preface to the Myth of Sisyphus; I anticipated the positive in all three forms again. Romance: The Plague. Drama: The State of Siege and The Righteous. Ideological: The Rebel. I already saw a third layer around the theme of love. These are the projects I have in progress

— Albert Camus at Stockholm in 1957, quoted by Roger Quilliot in Essais, II, p. 1610.

The cycle of the absurd, or negation, primarily addresses suicide and the human condition. It is expressed through four of Camus's works: the novel The Stranger and the essay The Myth of Sisyphus (1942), then the plays Caligula and The Misunderstanding (1944). By refusing the refuge of belief, Human becomes aware that his existence revolves around repetitive and meaningless acts. The certainty of death only reinforces, according to the writer, the feeling of uselessness of all existence. The absurd is therefore the feeling that man feels when confronted with the absence of meaning in the face of the Universe, the painful realization of his separation from the world. The question then arises of the legitimacy of suicide.

The cycle of revolt, called the positive, is a direct response to the absurd and is also expressed by four of his works: the novel The Plague (1947), the plays The State of Siege (1948) and The Just Assassins (1949), then the essay The Rebel (1951). Positive concept of affirmation of the individual, where only action and commitment count in the face of the tragedy of the world, revolt is for the writer the way of experiencing the absurd, knowing our fatal destiny and nevertheless facing it : "Man refuses the world as it is, without agreeing to escape it." It is intelligence grappling with the "unreasonable silence of the world". Depriving ourselves of eternal life frees us from the constraints imposed by an improbable future; Man gains freedom of action, lucidity and dignity.

The philosophy of Camus therefore has as its finitude a singular humanism. Advancing a message of lucidity, resilience and emancipation in the face of the absurdity of life, it encourages people to create their own meanings through personal choices and commitments, and to embrace their freedom to the fullest. Because he affirms that, even in the absurd, there is room for passion and rebellion; and although the Universe may be indifferent to our search for meaning, this search is in itself meaningful. In The Myth of Sisyphus, despite his absurd destiny, Sisyphus finds a form of liberation in his incessant work: "one must imagine Sisyphus happy". With the cycle of love and the "midday thought" (French: la pensée de midi), the philosophy of the absurd is completed by a principle of measurement and pleasure, close to Epicureanism.

Though the notion of the 'absurd' pervades all Albert Camus's writing, The Myth of Sisyphus is his chief work on the subject. In it, Camus considers absurdity as a confrontation, an opposition, a conflict or a "divorce" between two ideals. Specifically, he defines the human condition as absurd, as the confrontation between man's desire for significance, meaning and clarity on the one hand—and the silent, cold universe on the other. He continues that there are specific human experiences evoking notions of absurdity. Such a realization or encounter with the absurd leaves the individual with a choice: suicide, a leap of faith, or recognition. He concludes that recognition is the only defensible option.

For Camus, suicide is a "confession" that life is not worth living; it is a choice that implicitly declares that life is "too much." Suicide offers the most basic "way out" of absurdity: the immediate termination of the self and its place in the universe.

The absurd encounter can also arouse a "leap of faith," a term derived from one of Kierkegaard's early pseudonyms, Johannes de Silentio (although the term was not used by Kierkegaard himself), where one believes that there is more than the rational life (aesthetic or ethical). To take a "leap of faith," one must act with the "virtue of the absurd" (as Johannes de Silentio put it), where a suspension of the ethical may need to exist. This faith has no expectations, but is a flexible power initiated by a recognition of the absurd. Camus states that because the leap of faith escapes rationality and defers to abstraction over personal experience, the leap of faith is not absurd. Camus considers the leap of faith as "philosophical suicide," rejecting both this and physical suicide.

Lastly, a person can choose to embrace the absurd condition. According to Camus, one's freedom—and the opportunity to give life meaning—lies in the recognition of absurdity. If the absurd experience is truly the realization that the universe is fundamentally devoid of absolutes, then we as individuals are truly free. "To live without appeal," as he puts it, is a philosophical move to define absolutes and universals subjectively, rather than objectively. The freedom of man is thus established in one's natural ability and opportunity to create their own meaning and purpose; to decide (or think) for oneself. The individual becomes the most precious unit of existence, representing a set of unique ideals that can be characterized as an entire universe in its own right. In acknowledging the absurdity of seeking any inherent meaning, but continuing this search regardless, one can be happy, gradually developing meaning from the search alone. "Happiness and the absurd are two sons of the same earth. They are inseparable."

Camus states in The Myth of Sisyphus: "Thus I draw from the absurd three consequences, which are my revolt, my freedom, and my passion. By the mere activity of consciousness I transform into a rule of life what was an invitation to death, and I refuse suicide." "Revolt" here refers to the refusal of suicide and search for meaning despite the revelation of the Absurd; "Freedom" refers to the lack of imprisonment by religious devotion or others' moral codes; "Passion" refers to the most wholehearted experiencing of life, since hope has been rejected, and so he concludes that every moment must be lived fully.

Relation to other concepts

Existentialism and nihilism

Absurdism originated from (as well as alongside) the 20th-century strains of existentialism and nihilism; it shares some prominent starting points with both, though also entails conclusions that are uniquely distinct from these other schools of thought. All three arose from the human experience of anguish and confusion stemming from existence: the apparent meaninglessness of a world in which humans, nevertheless, are compelled to find or create meaning. The three schools of thought diverge from there. Existentialists have generally advocated the individual's construction of their own meaning in life as well as the free will of the individual. Nihilists, on the contrary, contend that "it is futile to seek or to affirm meaning where none can be found." Absurdists, following Camus' formulation, hesitantly allow the possibility for some meaning or value in life, but are neither as certain as existentialists are about the value of one's own constructed meaning nor as nihilists are about the total inability to create meaning. Absurdists following Camus also devalue or outright reject free will, encouraging merely that the individual live defiantly and authentically in spite of the psychological tension of the Absurd.

Camus himself passionately worked to counter nihilism, as he explained in his essay "The Rebel", while he also categorically rejected the label of "existentialist" in his essay "Enigma" and in the compilation The Lyrical and Critical Essays of Albert Camus, though he was, and still is, often broadly characterized by others as an existentialist. Both existentialism and absurdism entail consideration of the practical applications of becoming conscious of the truth of existential nihilism: i.e., how a driven seeker of meaning should act when suddenly confronted with the seeming concealment, or downright absence, of meaning in the universe.

While absurdism can be seen as a kind of response to existentialism, it can be debated exactly how substantively the two positions differ from each other. The existentialist, after all, does not deny the reality of death. But the absurdist seems to reaffirm the way in which death ultimately nullifies our meaning-making activities, a conclusion the existentialists seem to resist through various notions of posterity or, in Sartre's case, participation in a grand humanist project.

Existential crisis

The basic problem of absurdism is usually not encountered through a dispassionate philosophical inquiry but as the manifestation of an existential crisis. Existential crises are inner conflicts in which the individual wrestles with the impression that life lacks meaning. They are accompanied by various negative experiences, such as stress, anxiety, despair, and depression, which can disturb the individual's normal functioning in everyday life. In this sense, the conflict underlying the absurdist perspective poses a psychological challenge to the affected. This challenge is due to the impression that the agent's vigorous daily engagement stands in incongruity with its apparent insignificance encountered through philosophical reflection. Realizing this incongruity is usually not a pleasant occurrence and may lead to estrangement, alienation, and hopelessness. The intimate relation to psychological crises is also manifested in the problem of finding the right response to this unwelcome conflict, for example, by denying it, by taking life less seriously, or by revolting against the absurd. But accepting the position of absurdism may also have certain positive psychological effects. In this sense, it can help the individual achieve a certain psychological distance from unexamined dogmas and thus help them evaluate their situation from a more encompassing and objective perspective. However, it brings with it the danger of leveling all significant differences and thereby making it difficult for the individual to decide what to do or how to live their life.

Epistemological skepticism

It has been argued that absurdism in the practical domain resembles epistemological skepticism in the theoretical domain. In the case of epistemology, we usually take for granted our knowledge of the world around us even though, when methodological doubt is applied, it turns out that this knowledge is not as unshakable as initially assumed. For example, the agent may decide to trust their perception that the sun is shining but its reliability depends on the assumption that the agent is not dreaming, which they would not know even if they were dreaming. In a similar sense in the practical domain, the agent may decide to take aspirin in order to avoid a headache even though they may be unable to give a reason for why they should be concerned with their own wellbeing at all. In both cases, the agent goes ahead with a form of unsupported natural confidence and takes life largely for granted despite the fact that their power to justify is only limited to a rather small range and fails when applied to the larger context, on which the small range depends.

Education

It has been argued that absurdism is opposed to various fundamental principles and assumptions guiding education, like the importance of truth and of fostering rationality in the students.

Negative feedback

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Negative_feedback 

 

A simple negative feedback system is descriptive, for example, of some electronic amplifiers. The feedback is negative if the loop gain AB is negative.

Negative feedback (or balancing feedback) occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances.

Whereas positive feedback tends to instability via exponential growth, oscillation or chaotic behavior, negative feedback generally promotes stability. Negative feedback tends to promote a settling to equilibrium, and reduces the effects of perturbations. Negative feedback loops in which just the right amount of correction is applied with optimum timing, can be very stable, accurate, and responsive.

Negative feedback is widely used in mechanical and electronic engineering, and it is observed in many other fields including biology, chemistry and economics. General negative feedback systems are studied in control systems engineering.

Negative feedback loops also play an integral role in maintaining the atmospheric balance in various climate systems on Earth. One such feedback system is the interaction between solar radiation, cloud cover, and planet temperature.

Blood glucose levels are maintained at a constant level in the body by a negative feedback mechanism. When the blood glucose level is too high, the pancreas secretes insulin and when the level is too low, the pancreas then secretes glucagon. The flat line shown represents the homeostatic set point. The sinusoidal line represents the blood glucose level.

General description

Feedback loops in the human body

In many physical and biological systems, qualitatively different influences can oppose each other. For example, in biochemistry, one set of chemicals drives the system in a given direction, whereas another set of chemicals drives it in an opposing direction. If one or both of these opposing influences are non-linear, equilibrium point(s) result.

In biology, this process (in general, biochemical) is often referred to as homeostasis; whereas in mechanics, the more common term is equilibrium.

In engineering, mathematics and the physical, and biological sciences, common terms for the points around which the system gravitates include: attractors, stable states, eigenstates/eigenfunctions, equilibrium points, and setpoints.

In control theory, negative refers to the sign of the multiplier in mathematical models for feedback. In delta notation, −Δoutput is added to or mixed into the input. In multivariate systems, vectors help to illustrate how several influences can both partially complement and partially oppose each other.

Some authors, in particular with respect to modelling business systems, use negative to refer to the reduction in difference between the desired and actual behavior of a system. In a psychology context, on the other hand, negative refers to the valence of the feedback – attractive versus aversive, or praise versus criticism.

In contrast, positive feedback is feedback in which the system responds so as to increase the magnitude of any particular perturbation, resulting in amplification of the original signal instead of stabilization. Any system in which there is positive feedback together with a gain greater than one will result in a runaway situation. Both positive and negative feedback require a feedback loop to operate.

However, negative feedback systems can still be subject to oscillations. This is caused by a phase shift around any loop. Due to these phase shifts the feedback signal of some frequencies can ultimately become in phase with the input signal and thus turn into positive feedback, creating a runaway condition. Even before the point where the phase shift becomes 180 degrees, stability of the negative feedback loop will become compromised, leading to increasing under- and overshoot following a disturbance. This problem is often dealt with by attenuating or changing the phase of the problematic frequencies in a design step called compensation. Unless the system naturally has sufficient damping, many negative feedback systems have low pass filters or dampers fitted.

Examples

• Mercury thermostats (circa 1600) using expansion and contraction of columns of mercury in response to temperature changes were used in negative feedback systems to control vents in furnaces, maintaining a steady internal temperature.
• In the invisible hand of the market metaphor of economic theory (1776), reactions to price movements provide a feedback mechanism to match supply and demand.
• In centrifugal governors (1788), negative feedback is used to maintain a near-constant speed of an engine, irrespective of the load or fuel-supply conditions.
• In a steering engine (1866), power assistance is applied to the rudder with a feedback loop, to maintain the direction set by the steersman.
• In servomechanisms, the speed or position of an output, as determined by a sensor, is compared to a set value, and any error is reduced by negative feedback to the input.
• In audio amplifiers, negative feedback flattens frequency response, reduces distortion, minimises the effect of manufacturing variations in component parameters, and compensates for changes in characteristics due to temperature change.
• In analog computing, feedback around operational amplifiers is used to generate mathematical functions such as addition, subtraction, integration, differentiation, logarithm, and antilog functions.
• In delta-sigma analog-to-digital and digital-to-analog converters (particularly for high quality audio), a negative feedback loop is used to repeatedly correct accumulated quantization error during conversion.
• In a phase locked loop (1932), feedback is used to maintain a generated alternating waveform in a constant phase to a reference signal. In many implementations the generated waveform is the output, but when used as a demodulator in an FM radio receiver, the error feedback voltage serves as the demodulated output signal. If there is a frequency divider between the generated waveform and the phase comparator, the device acts as a frequency multiplier.
• In organisms, feedback enables various measures (e.g. body temperature, or blood sugar level) to be maintained within a desired range by homeostatic processes.

Detailed implementations

Error-controlled regulation

Basic error-controlled regulator loop

See also: Control engineering, Homeostasis, and Allostasis

A regulator R adjusts the input to a system T so the monitored essential variables E are held to set-point values S that result in the desired system output despite disturbances D.

One use of feedback is to make a system (say T) self-regulating to minimize the effect of a disturbance (say D). Using a negative feedback loop, a measurement of some variable (for example, a process variable, say E) is subtracted from a required value (the 'set point') to estimate an operational error in system status, which is then used by a regulator (say R) to reduce the gap between the measurement and the required value. The regulator modifies the input to the system T according to its interpretation of the error in the status of the system. This error may be introduced by a variety of possible disturbances or 'upsets', some slow and some rapid. The regulation in such systems can range from a simple 'on-off' control to a more complex processing of the error signal.

In this framework, the physical form of a signal may undergo multiple transformations. For example, a change in weather may cause a disturbance to the heat input to a house (as an example of the system T) that is monitored by a thermometer as a change in temperature (as an example of an 'essential variable' E). This quantity, then, is converted by the thermostat (a 'comparator') into an electrical error in status compared to the 'set point' S, and subsequently used by the regulator (containing a 'controller' that commands gas control valves and an ignitor) ultimately to change the heat provided by a furnace (an 'effector') to counter the initial weather-related disturbance in heat input to the house.

Error controlled regulation is typically carried out using a Proportional-Integral-Derivative Controller (PID controller). The regulator signal is derived from a weighted sum of the error signal, integral of the error signal, and derivative of the error signal. The weights of the respective components depend on the application.

Mathematically, the regulator signal is given by:

${\displaystyle \mathrm{M}\mathrm{V}(\mathrm{t})=K_p\left(e(t)+\frac{1}{T_i}{\int }_0^{t}e(\tau )d\tau +T_d\frac{d}{dt}e(t)\right)}$

where

${\displaystyle T_i}$ is the integral time

${\displaystyle T_d}$ is the derivative time

Negative feedback amplifier

Main article: Negative-feedback amplifier

The negative feedback amplifier was invented by Harold Stephen Black at Bell Laboratories in 1927, and granted a patent in 1937 (US Patent 2,102,671) "a continuation of application Serial No. 298,155, filed August 8, 1928 ...").

"The patent is 52 pages long plus 35 pages of figures. The first 43 pages amount to a small treatise on feedback amplifiers!"

There are many advantages to feedback in amplifiers. In design, the type of feedback and amount of feedback are carefully selected to weigh and optimize these various benefits.

Advantages of amplifier negative voltage feedback

Negative voltage feedback in amplifiers has the following advantages; it

1. reduces non-linear distortion, i.e., produces higher fidelity;
2. increases circuit stability: i.e., gains remain stable over variations in ambient temperature, frequency, and signal amplitude;
3. slightly increases bandwidth;
4. modifies input and output impedances;
5. considerably reduces harmonic, phase, amplitude, and frequency distortions; and
6. considerably reduces noise.

Though negative feedback has many advantages, amplifiers with feedback can oscillate (see Step response of feedback amplifiers), and they may exhibit instability. Harry Nyquist of Bell Laboratories proposed the a stability criterion and a plot to identify stable feedback systems, including amplifiers and control systems.

Negative feedback amplifier with external disturbance. The feedback is negative if βA >0.

The figure shows a simplified block diagram of a negative feedback amplifier.

The feedback sets the overall (closed-loop) amplifier gain at a value:

${\displaystyle \frac{O}{I}=\frac{A}{1+\beta A}\approx \frac{1}{\beta },}$

where the approximate value assumes βA >> 1. This expression shows that a gain greater than one requires β < 1. Because the approximate gain 1/β is independent of the open-loop gain A, the feedback is said to 'desensitize' the closed-loop gain to variations in A (for example, due to manufacturing variations between units, or temperature effects upon components), provided only that the gain A is sufficiently large. In this context, the factor (1+βA) is often called the 'desensitivity factor', and in the broader context of feedback effects that include other matters like electrical impedance and bandwidth, the 'improvement factor'.

If the disturbance D is included, the amplifier output becomes:

${\displaystyle O=\frac{AI}{1+\beta A}+\frac{D}{1+\beta A},}$

which shows that the feedback reduces the effect of the disturbance by the 'improvement factor' (1+β A). The disturbance D might arise from fluctuations in the amplifier output due to noise and nonlinearity (distortion) within this amplifier, or from other noise sources such as power supplies.

The difference signal I–βO at the amplifier input is sometimes called the "error signal". According to the diagram, the error signal is:

${\displaystyle \text{Error signal}=I-\beta O=I\left(1-\beta \frac{O}{I}\right)=\frac{I}{1+\beta A}-\frac{\beta D}{1+\beta A}.}$

From this expression, it can be seen that a large 'improvement factor' (or a large loop gain βA) tends to keep this error signal small.

Although the diagram illustrates the principles of the negative feedback amplifier, modeling a real amplifier as a unilateral forward amplification block and a unilateral feedback block has significant limitations. For methods of analysis that do not make these idealizations, see the article Negative feedback amplifier.

Operational amplifier circuits

Main article: Operational amplifier applications

A feedback voltage amplifier using an op amp with finite gain but infinite input impedances and zero output impedance.

The operational amplifier was originally developed as a building block for the construction of analog computers, but is now used almost universally in all kinds of applications including audio equipment and control systems.

Operational amplifier circuits typically employ negative feedback to get a predictable transfer function. Since the open-loop gain of an op-amp is extremely large, a small differential input signal would drive the output of the amplifier to one rail or the other in the absence of negative feedback. A simple example of the use of feedback is the op-amp voltage amplifier shown in the figure.

The idealized model of an operational amplifier assumes that the gain is infinite, the input impedance is infinite, output resistance is zero, and input offset currents and voltages are zero. Such an ideal amplifier draws no current from the resistor divider. Ignoring dynamics (transient effects and propagation delay), the infinite gain of the ideal op-amp means this feedback circuit drives the voltage difference between the two op-amp inputs to zero. Consequently, the voltage gain of the circuit in the diagram, assuming an ideal op amp, is the reciprocal of feedback voltage division ratio β:

${\displaystyle V_{\text{out}}=\frac{R_{\text{1}}+R_{\text{2}}}{R_{\text{1}}}{V}_{\text{in}}=\frac{1}{\beta }{V}_{\text{in}}}$.

A real op-amp has a high but finite gain A at low frequencies, decreasing gradually at higher frequencies. In addition, it exhibits a finite input impedance and a non-zero output impedance. Although practical op-amps are not ideal, the model of an ideal op-amp often suffices to understand circuit operation at low enough frequencies. As discussed in the previous section, the feedback circuit stabilizes the closed-loop gain and desensitizes the output to fluctuations generated inside the amplifier itself.

Areas of application

Mechanical engineering

See also: Control systems and Control engineering

The ballcock or float valve uses negative feedback to control the water level in a cistern.

An example of the use of negative feedback control is the ballcock control of water level (see diagram), or a pressure regulator. In modern engineering, negative feedback loops are found in engine governors, fuel injection systems and carburettors. Similar control mechanisms are used in heating and cooling systems, such as those involving air conditioners, refrigerators, or freezers.

Biology

See also: Counterregulatory hormone and Homeostasis

Control of endocrine hormones by negative feedback.

Some biological systems exhibit negative feedback such as the baroreflex in blood pressure regulation and erythropoiesis. Many biological processes (e.g., in the human anatomy) use negative feedback. Examples of this are numerous, from the regulating of body temperature, to the regulating of blood glucose levels. The disruption of feedback loops can lead to undesirable results: in the case of blood glucose levels, if negative feedback fails, the glucose levels in the blood may begin to rise dramatically, thus resulting in diabetes.

For hormone secretion regulated by the negative feedback loop: when gland X releases hormone X, this stimulates target cells to release hormone Y. When there is an excess of hormone Y, gland X "senses" this and inhibits its release of hormone X. As shown in the figure, most endocrine hormones are controlled by a physiologic negative feedback inhibition loop, such as the glucocorticoids secreted by the adrenal cortex. The hypothalamus secretes corticotropin-releasing hormone, which directs the anterior pituitary gland to secrete adrenocorticotropic hormone (ACTH). In turn, ACTH directs the adrenal cortex to secrete glucocorticoids, such as cortisol. Glucocorticoids not only perform their respective functions throughout the body but also negatively affect the release of further stimulating secretions of both the hypothalamus and the pituitary gland, effectively reducing the output of glucocorticoids once a sufficient amount has been released.

Chemistry

Closed systems containing substances undergoing a reversible chemical reaction can also exhibit negative feedback in accordance with Le Chatelier's principle which shift the chemical equilibrium to the opposite side of the reaction in order to reduce a stress. For example, in the reaction

N₂ + 3 H₂ ⇌ 2 NH₃ + 92 kJ/mol

If a mixture of the reactants and products exists at equilibrium in a sealed container and nitrogen gas is added to this system, then the equilibrium will shift toward the product side in response. If the temperature is raised, then the equilibrium will shift toward the reactant side which, since the reverse reaction is endothermic, will partially reduce the temperature.

Self-organization

Main articles: Self-organization and Emergence

Self-organization is the capability of certain systems "of organizing their own behavior or structure". There are many possible factors contributing to this capacity, and most often positive feedback is identified as a possible contributor. However, negative feedback also can play a role.

Economics

In economics, automatic stabilisers are government programs that are intended to work as negative feedback to dampen fluctuations in real GDP.

Mainstream economics asserts that the market pricing mechanism operates to match supply and demand, because mismatches between them feed back into the decision-making of suppliers and demanders of goods, altering prices and thereby reducing any discrepancy. However Norbert Wiener wrote in 1948:

"There is a belief current in many countries and elevated to the rank of an official article of faith in the United States that free competition is itself a homeostatic process... Unfortunately the evidence, such as it is, is against this simple-minded theory."

The notion of economic equilibrium being maintained in this fashion by market forces has also been questioned by numerous heterodox economists such as financier George Soros and leading ecological economist and steady-state theorist Herman Daly, who was with the World Bank in 1988–1994.

Environmental science

Some effects of climate change can either enhance (positive feedbacks) or weaken (negative feedbacks) global warming.

A basic and common example of a negative feedback system in the environment is the interaction among cloud cover, plant growth, solar radiation, and planet temperature. As incoming solar radiation increases, planet temperature increases. As the temperature increases, the amount of plant life that can grow increases. This plant life can then make products such as sulfur which produce more cloud cover. An increase in cloud cover leads to higher albedo, or surface reflectivity, of the Earth. As albedo increases, however, the amount of solar radiation decreases. This, in turn, affects the rest of the cycle.

Cloud cover, and in turn planet albedo and temperature, is also influenced by the hydrological cycle. As planet temperature increases, more water vapor is produced, creating more clouds. The clouds then block incoming solar radiation, lowering the temperature of the planet. This interaction produces less water vapor and therefore less cloud cover. The cycle then repeats in a negative feedback loop. In this way, negative feedback loops in the environment have a stabilizing effect.

History

Negative feedback as a control technique may be seen in the refinements of the water clock introduced by Ktesibios of Alexandria in the 3rd century BCE. Self-regulating mechanisms have existed since antiquity, and were used to maintain a constant level in the reservoirs of water clocks as early as 200 BCE.

The fly-ball governor, an early example of negative feedback

Negative feedback was implemented in the 17th century. Cornelius Drebbel had built thermostatically controlled incubators and ovens in the early 1600s, and centrifugal governors were used to regulate the distance and pressure between millstones in windmills. James Watt patented a form of governor in 1788 to control the speed of his steam engine, and James Clerk Maxwell in 1868 described "component motions" associated with these governors that lead to a decrease in a disturbance or the amplitude of an oscillation.

The term "feedback" was well established by the 1920s, in reference to a means of boosting the gain of an electronic amplifier. Friis and Jensen described this action as "positive feedback" and made passing mention of a contrasting "negative feed-back action" in 1924. Harold Stephen Black came up with the idea of using negative feedback in electronic amplifiers in 1927, submitted a patent application in 1928, and detailed its use in his paper of 1934, where he defined negative feedback as a type of coupling that reduced the gain of the amplifier, in the process greatly increasing its stability and bandwidth.

Karl Küpfmüller published papers on a negative-feedback-based automatic gain control system and a feedback system stability criterion in 1928.

Nyquist and Bode built on Black's work to develop a theory of amplifier stability.

Early researchers in the area of cybernetics subsequently generalized the idea of negative feedback to cover any goal-seeking or purposeful behavior.

All purposeful behavior may be considered to require negative feed-back. If a goal is to be attained, some signals from the goal are necessary at some time to direct the behavior.

Cybernetics pioneer Norbert Wiener helped to formalize the concepts of feedback control, defining feedback in general as "the chain of the transmission and return of information", and negative feedback as the case when:

The information fed back to the control center tends to oppose the departure of the controlled from the controlling quantity...^: 97

While the view of feedback as any "circularity of action" helped to keep the theory simple and consistent, Ashby pointed out that, while it may clash with definitions that require a "materially evident" connection, "the exact definition of feedback is nowhere important". Ashby pointed out the limitations of the concept of "feedback":

The concept of 'feedback', so simple and natural in certain elementary cases, becomes artificial and of little use when the interconnections between the parts become more complex...Such complex systems cannot be treated as an interlaced set of more or less independent feedback circuits, but only as a whole. For understanding the general principles of dynamic systems, therefore, the concept of feedback is inadequate in itself. What is important is that complex systems, richly cross-connected internally, have complex behaviors, and that these behaviors can be goal-seeking in complex patterns.^: 54

To reduce confusion, later authors have suggested alternative terms such as degenerative, self-correcting, balancing, or discrepancy-reducing in place of "negative".