A conspiracy theory is an explanation of an event or situation that invokes a conspiracy by sinister and powerful actors, often political in motivation,^[5][6] when other explanations are more probable.^[7] The term has a pejorative connotation, implying that the appeal to a conspiracy is based on prejudice or insufficient evidence.^[8] Conspiracy theories resist falsification and are reinforced by circular reasoning: both evidence against the conspiracy and an absence of evidence for it, are re-interpreted as evidence of its truth,^[8][9] and the conspiracy becomes a matter of faith rather than proof.^[10][11]

Research suggests, on a psychological level, conspiracist ideation—belief in conspiracy theories—can be harmful or pathological,^[12][13] and is highly correlated with psychological projection, as well as with paranoia, which is predicted by the degree of a person's Machiavellianism.^[14] Conspiracy theories once limited to fringe audiences have become commonplace in mass media, emerging as a cultural phenomenon of the late 20th and early 21st centuries.^{[15][16][17][18]}

The Oxford English Dictionary defines conspiracy theory as "the theory that an event or phenomenon occurs as a result of a conspiracy between interested parties; spec. a belief that some covert but influential agency (typically political in motivation and oppressive in intent) is responsible for an unexplained event". It cites a 1909 article in The American Historical Review as the earliest usage example,^[19][20] although it also appears in journals as early as April 1870.^[21] The word "conspiracy" derives from the Latin con- ("with, together") and spirare ("to breathe").

Robert Blaskiewicz notes examples of the term were used as early as the nineteenth century and states that its usage has always been derogatory.^[22] Lance deHaven-Smith suggested that the term entered everyday language in the United States after 1964, the year in which the Warren Commission shared its findings, with The New York Times running five stories that year using the term.^[23]

A conspiracy theory is not simply a conspiracy. Barkun writes that conspiracies are "actual covert plots planned and/or carried out by two or more persons". A conspiracy theory, on the other hand, is "an intellectual construct", a "template imposed upon the world to give the appearance of order to events". Positing that "some small and hidden group" has manipulated events, a conspiracy theory can be local or international, focused on single events or covering multiple incidents and entire countries, regions and periods of history. Conspiracy theorists see themselves as having privileged access to special knowledge or a special mode of thought that separates them from the masses who believe the official account.^[24]

A conspiracy theory may take any matter as its subject, but certain subjects attract greater interest than others. Favored subjects include famous deaths, government activities, new technologies, terrorism, and questions of alien life. Among the longest-standing and most widely recognized conspiracy theories are notions concerning the assassination of John F. Kennedy, the 1969 Apollo moon landings, and the 9/11 terrorist attacks, as well as numerous theories pertaining to alleged plots for world domination by various groups both real and imaginary.^[25]

Some scholars argue that conspiracy theories once limited to fringe audiences have become commonplace in mass media, contributing to conspiracism emerging as a cultural phenomenon in the United States of the late 20th and early 21st centuries.^{[15][16][17][18]} According to anthropologists Todd Sanders and Harry G. West, evidence suggests that a broad cross-section of Americans today gives credence to at least some conspiracy theories.^[26] For instance, a study conducted in 2016 found that 10% of Americans think the chemtrail conspiracy theory is "completely true" and 20-30% think it is "somewhat true".^[27] This puts "the equivalent of 120 million Americans in the “chemtrails are real” camp.^[27] Belief in conspiracy theories has therefore become a topic of interest for sociologists, psychologists and experts in folklore.

Conspiracy theories are widely present on the Web in the form of blogs and YouTube videos, as well as on social media. Whether the Web has increased the prevalence of conspiracy theories or not is an open research question.^[28] The presence and representation of conspiracy theories in search engine results has been monitored and studied, showing significant variation across different topics, and a general absence of reputable, high-quality links in the results.^[29]

Jesse Walker (2013) has identified five kinds of conspiracy theories:

Michael Barkun has identified three classifications of conspiracy theory:

Murray Rothbard argues in favor of a model that contrasts "deep" conspiracy theories to "shallow" ones. According to Rothbard, a "shallow" theorist observes an event and asks Cui bono? ("Who benefits?"), jumping to the conclusion that a posited beneficiary is responsible for covertly influencing events. On the other hand, the "deep" conspiracy theorist begins with a hunch and then seeks out evidence. Rothbard describes this latter activity as a matter of confirming with certain facts one's initial paranoia.^[32]

Belief in conspiracy theories is generally based not on evidence, but in the faith of the believer.^[33] Noam Chomsky contrasts conspiracy theory to institutional analysis which focuses mostly on the public, long-term behavior of publicly known institutions, as recorded in, for example, scholarly documents or mainstream media reports.^[34] Conspiracy theory conversely posits the existence of secretive coalitions of individuals and speculates on their alleged activities.^[35][36]

Clare Birchall at King's College London describes conspiracy theory as a "form of popular knowledge or interpretation".^[1] The use of the word 'knowledge' here suggests ways in which conspiracy theory may be considered in relation to legitimate modes of knowing.^[2] The relationship between legitimate and illegitimate knowledge, Birchall claims, is closer than common dismissals of conspiracy theory contend.^[38]

Theories involving multiple conspirators that are proven to be correct, such as the Watergate scandal, are usually referred to as "investigative journalism" or "historical analysis" rather than conspiracy theory.^[39] By contrast, the term "Watergate conspiracy theory" is used to refer to a variety of hypotheses in which those convicted in the conspiracy were in fact the victims of a deeper conspiracy.^[40]

The historian Richard Hofstadter addressed the role of paranoia and conspiracism throughout U.S. history in his 1964 essay "The Paranoid Style in American Politics". Bernard Bailyn's classic The Ideological Origins of the American Revolution (1967) notes that a similar phenomenon could be found in North America during the time preceding the American Revolution. Conspiracism labels people's attitudes as well as the type of conspiracy theories that are more global and historical in proportion.^[41]

The term "conspiracism" was further popularized by academic Frank P. Mintz in the 1980s. According to Mintz, conspiracism denotes "belief in the primacy of conspiracies in the unfolding of history":^{[42] []}

Justin Fox of Time magazine is of the opinion that Wall Street traders are among the most conspiracy-minded group of people, and ascribes this to the reality of some financial market conspiracies, and to the ability of conspiracy theories to provide necessary orientation in the market's day-to-day movements. He believes as well that most good investigative reporters are also conspiracy theorists.^[43]

Matthew Gray has noted that conspiracy theories are a prevalent feature of Arab culture and politics.^[44] Variants include conspiracies involving colonialism, Zionism, superpowers, oil, and the war on terrorism, which may be referred to as a war against Islam.^[44] For example, The Protocols of the Elders of Zion, an infamous hoax document purporting to be a Jewish plan for world domination, is commonly read and promoted in the Muslim world.^[45][46][47] Roger Cohen has suggested that the popularity of conspiracy theories in the Arab world is "the ultimate refuge of the powerless".^[48] Al-Mumin Said has noted the danger of such theories, for they "keep us not only from the truth but also from confronting our faults and problems".^[49]

Harry G. West and others have noted that while conspiracy theorists may often be dismissed as a fringe minority, certain evidence suggests that a wide range of the U.S. maintains a belief in conspiracy theories. West also compares those theories to hypernationalism and religious fundamentalism.^[50][51]

Theologian Robert Jewett and philosopher John Shelton Lawrence attribute the enduring popularity of conspiracy theories in the U.S. to the Cold War, McCarthyism, and counterculture rejection of authority. They state that among both the left-wing and right-wing, there remains a willingness to use real events, such as Soviet plots, inconsistencies in the Warren Report, and the 9/11 attacks, to support the existence of unverified and ongoing large-scale conspiracies.^[52]

The Watergate scandal has also been used to bestow legitimacy to other conspiracy theories, with Richard Nixon himself commenting that it served as a "Rorschach ink blot" which invited others to fill in the underlying pattern.^[39]

Historian Kathryn S. Olmstead cites three reasons why Americans are prone to believing in government conspiracies theories:

The widespread belief in conspiracy theories has become a topic of interest for sociologists, psychologists, and experts in folklore since at least the 1960s, when a number of conspiracy theories arose regarding the assassination of U.S. President John F. Kennedy. Sociologist Türkay Salim Nefes underlines the political nature of conspiracy theories. He suggests that one of the most important characteristics of these accounts is their attempt to unveil the "real but hidden" power relations in social groups.^[54][55]

The political scientist Michael Barkun, discussing the usage of "conspiracy theory" in contemporary American culture, holds that this term is used for a belief that explains an event as the result of a secret plot by exceptionally powerful and cunning conspirators to achieve a malevolent end.^[56][57] According to Barkun, the appeal of conspiracism is threefold:

This third point is supported by research of Roland Imhoff, professor in Social Psychology at the Johannes Gutenberg University Mainz. The research suggests that the smaller the minority believing in a specific theory, the more attractive it is to conspiracy theorists.^[58]

Humanistic psychologists argue that even if a posited cabal behind an alleged conspiracy is almost always perceived as hostile, there often remains an element of reassurance for theorists. This is because it is a consolation to imagine that difficulties in human affairs are created by humans, and remain within human control. If a cabal can be implicated, there may be a hope of breaking its power or of joining it. Belief in the power of a cabal is an implicit assertion of human dignity—an unconscious affirmation that man is responsible for his own destiny.^[59]

People formulate conspiracy theories to explain, for example, power relations in social groups and the perceived existence of evil forces.^{[3][57][54][55]} Proposed psychological origins of conspiracy theorising include projection; the personal need to explain "a significant event [with] a significant cause;" and the product of various kinds and stages of thought disorder, such as paranoid disposition, ranging in severity to diagnosable mental illnesses. Some people prefer socio-political explanations over the insecurity of encountering random, unpredictable, or otherwise inexplicable events.^{[43][60][61][62][63][48]}

According to Berlet and Lyons, "Conspiracism is a particular narrative form of scapegoating that frames demonized enemies as part of a vast insidious plot against the common good, while it valorizes the scapegoater as a hero for sounding the alarm".^[64]

Some psychologists believe that a search for meaning is common in conspiracism. Once cognized, confirmation bias and avoidance of cognitive dissonance may reinforce the belief. In a context where a conspiracy theory has become embedded within a social group, communal reinforcement may also play a part.^[65]

Some historians have argued that there is an element of psychological projection in conspiracism. This projection, according to the argument, is manifested in the form of attribution of undesirable characteristics of the self to the conspirators. Historian Richard Hofstadter stated that:

Hofstadter also noted that "sexual freedom" is a vice frequently attributed to the conspiracist's target group, noting that "very often the fantasies of true believers reveal strong sadomasochistic outlets, vividly expressed, for example, in the delight of anti-Masons with the cruelty of Masonic punishments."^[62]

Christopher Hitchens described conspiracy theory as the "exhaust fumes of democracy":^[63] the unavoidable result of a large amount of information circulating among a large number of people.

Conspiracy theories may be emotionally satisfying, by assigning blame to a group to which the theorist does not belong and so absolving the theorist of moral or political responsibility in society.^[66] Likewise, Roger Cohen writing for The New York Times has said that, "captive minds; ... resort to conspiracy theory because it is the ultimate refuge of the powerless. If you cannot change your own life, it must be that some greater force controls the world."^[48]

Sociological historian Holger Herwig found in studying German explanations for the origins of World War I, "Those events that are most important are hardest to understand because they attract the greatest attention from myth makers and charlatans."^[67]

French sociologist Bruno Latour suggests that the widespread popularity of conspiracy theories in mass culture may be due, in part, to the pervasive presence of Marxist-inspired critical theory and similar ideas in academia since the 1970s.^[68]

Latour notes that about 90% of contemporary social criticism in academia displays one of two approaches, which he terms "the fact position and the fairy position".^{[68] []} The fairy position is anti-fetishist, arguing that "objects of belief" (e.g., religion, arts) are merely concepts onto which power is projected; Latour contends that those who use this approach show biases towards confirming their own dogmatic suspicions as most "scientifically supported". While the complete facts of the situation and correct methodology are ostensibly important to them, Latour proposes that the scientific process is instead laid on as a patina to one's pet theories to lend a sort of reputation high ground. The "fact position" argues that individuals are dominated, often covertly and without their awareness, by external forces (e.g., economics, gender).^[68] Latour concludes that each of these two approaches in Academia has led to a polarized, inefficient atmosphere highlighted (in both approaches) by its causticness. "Do you see now why it feels so good to be a critical mind?" asks Latour: no matter which position you take, "You're always right!"^[68]

Latour notes that such social criticism has been appropriated by those he describes as conspiracy theorists, including climate change denialists and the 9/11 Truth movement: "Maybe I am taking conspiracy theories too seriously, but I am worried to detect, in those mad mixtures of knee-jerk disbelief, punctilious demands for proofs, and free use of powerful explanation from the social neverland, many of the weapons of social critique."^[68]

Michael Kelly, a Washington Post journalist and critic of anti-war movements on both the left and right, coined the term "fusion paranoia" to refer to a political convergence of left-wing and right-wing activists around anti-war issues and civil liberties, which he said were motivated by a shared belief in conspiracism or shared anti-government views.^[69]

Barkun has adopted this term to refer to how the synthesis of paranoid conspiracy theories, which were once limited to American fringe audiences, has given them mass appeal and enabled them to become commonplace in mass media,^[70] thereby inaugurating an unrivaled period of people actively preparing for apocalyptic or millenarian scenarios in the United States of the late 20th and early 21st centuries.^[71] Barkun notes the occurrence of lone-wolf conflicts with law enforcement acting as proxy for threatening the established political powers.^[72]

The physicist David Robert Grimes estimated the time it would take for a conspiracy to be exposed based on the number of people involved.^[73][74] His calculations used data from the PRISM surveillance program, the Tuskegee syphilis experiment, and the FBI forensic scandal. Grimes estimated that:

In his book The Open Society and Its Enemies, the philosopher Karl Popper used the term "the conspiracy theory of society" to denote a conception of social phenomena that he found to be defective—namely, that social phenomena such as "war, unemployment, poverty, shortages ... [are] the result of direct design by some powerful individuals and groups."^[75] Popper argued that totalitarianism was founded on "conspiracy theories" which drew on imaginary plots driven by paranoid scenarios predicated on tribalism, chauvinism, or racism. Popper acknowledged that genuine conspiracies do exist,^[76] but noted how infrequently conspirators have been able to achieve their goal.^[76]

The historian Bruce Cumings similarly rejects the notion that history is controlled by conspiracies, stating that where real conspiracies have appeared they have usually had little effect on history and have had unforeseen consequences for the conspirators. Cumings concludes that history is instead "moved by the broad forces and large structures of human collectivities".^[77]

In a 2009 article, the legal scholars Cass Sunstein and Adrian Vermeule considered a number of possible government responses to conspiracy theories, including censorship and taxation. They concluded that the authorities ought to engage in counter-speech and dialogue, which they termed "cognitive infiltration".^[78]