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Extraordinary claims require extraordinary evidence

"Extraordinary claims require extraordinary evidence" is an aphorism in scientific skepticism and epistemology positing that propositions substantially at odds with well-established empirical knowledge or uniform human experience demand evidentiary support of commensurate strength to warrant belief.^[1] The principle underscores the role of prior probabilities in assessing claims, where assertions of low antecedent likelihood—such as violations of known physical laws—require robust, replicable data to shift credence, aligning with probabilistic reasoning frameworks like Bayes' theorem.^[2] Popularized by astronomer Carl Sagan in works like his 1980 television series Cosmos and 1995 book The Demon-Haunted World, the formulation echoes earlier expressions, including sociologist Marcello Truzzi's 1978 variant "extraordinary claims require extraordinary proof" in the context of parapsychology investigations.^[1]^[2] Its philosophical roots trace to David Hume's 1748 essay "Of Miracles," which contends that testimonial evidence for events contravening invariable natural laws must be intrinsically more improbable in its falsehood than the alleged event itself to be credible.^[3] While advocated to combat pseudoscience and unfounded assertions, the maxim has drawn critique for potentially conflating evidential thresholds with subjective priors, with some arguing that all claims are evaluated by ordinary standards of reliability rather than calibrated "extraordinariness."^[1]

Definition and Formulation

Core Statement and Variants

The principle that "extraordinary claims require extraordinary evidence" asserts that propositions contradicting well-established knowledge demand a higher threshold of supporting data than mundane assertions, reflecting the need for evidence strength proportional to a claim's deviation from prior expectations.^[1] This formulation, often termed the Sagan standard, was articulated by astronomer Carl Sagan in 1977, emphasizing rigorous scrutiny in scientific inquiry to counter pseudoscience and unfounded assertions.^[2] Earlier philosophical variants trace to David Hume's 1748 essay "Of Miracles," where he argued that "a wise man... proportions his belief to the evidence," and that miracle testimonies fail unless their falsity would exceed the miracle's improbability in violating uniform experience.^[3] Similarly, Pierre-Simon Laplace in 1810 stated, "The more extraordinary a fact, the stronger the proofs needed to establish it," or equivalently, "the weight of evidence for an extraordinary claim must be proportioned to its strangeness," grounding the idea in probabilistic reasoning against improbable events like miracles.^[2] Laplace's version, from his Philosophical Essay on Probabilities, underscores that evidence must counterbalance a claim's inherent low prior probability derived from empirical regularities.^[2] Pre-18th-century expressions include Benjamin Bayly's 1708 remark that extraordinary matters "will require a very extraordinary proof," and a 1738 publication demanding "extraordinary Evidence" for unusual reports.^[2] In 1740, Arthur Ashley Sykes asserted a right to "extraordinary evidence for any extraordinary fact."^[2] Sociologist Marcello Truzzi, in 1975, used "extraordinary claims require extraordinary proof," predating Sagan's popularization but aligning with skeptical methodologies.^[2] These variants collectively illustrate a longstanding epistemic norm: belief calibration to evidential robustness, particularly for claims challenging causal laws or accumulated observations.^[1]

Interpretation of "Extraordinary"

The term "extraordinary" in the principle "extraordinary claims require extraordinary evidence" is most rigorously interpreted through a Bayesian lens, where it denotes claims with exceptionally low prior probabilities derived from background empirical knowledge.^[4] In this framework, prior probability represents the baseline plausibility of a hypothesis before considering new data; claims that contravene well-corroborated scientific laws or patterns—such as violations of conservation of energy or causality—assign priors approaching zero, necessitating evidence whose likelihood ratio strongly favors the hypothesis over alternatives to elevate the posterior probability to a credible level.^[5]^[6] This probabilistic interpretation aligns with causal realism, emphasizing that "extraordinary" reflects not subjective astonishment but the objective improbability grounded in repeated observations of natural regularities; for instance, a claim of perpetual motion would demand experimental demonstrations exceeding the cumulative evidence for thermodynamic laws, accumulated over centuries of precise measurements.^[4] Philosophically, David Hume anticipated this in his 1748 essay "Of Miracles," defining extraordinary claims as those "contrary to experience" that overbalance uniform human testimony against them only if the supporting evidence exhibits a disproportional strength, such as multiple independent, highly reliable attestations outweighing the experiential prior.^[7] Critics of looser interpretations argue that "extraordinary" does not imply an arbitrary threshold of evidential novelty but rather proportionality: ordinary claims (high priors, like everyday mechanical failures) suffice with routine evidence, while extraordinary ones require the evidence's diagnostic power to compensate for inherent skepticism rooted in empirical priors.^[6] Misapplications, such as equating "extraordinary evidence" solely with volume or rarity without Bayesian calibration, can lead to undue dismissal of incrementally supported hypotheses, as seen in debates over non-local perception where standard statistical significance fails to address low priors without likelihood adjustments.^[4] Thus, the principle underscores evidence quality calibrated to claim improbability, prioritizing causal mechanisms verifiable through controlled replication over anecdotal or testimonial support.^[5]

Historical Origins

Philosophical Precursors

David Hume's 1748 essay "Of Miracles," part of An Enquiry Concerning Human Understanding, provides the foundational philosophical argument akin to the principle that extraordinary claims require extraordinary evidence. Hume defines a miracle as a violation of the laws of nature, established through uniform human experience, and contends that testimony supporting such an event must overcome the improbability inherent in defying this experience. He asserts: "A miracle is a violation of the laws of nature; and as a firm and unalterable experience has established these laws, the proof against a miracle, from the very nature of the fact, is as entire as any argument from experience can possibly be imagined."^[3] Hume further specifies the evidentiary threshold: "No testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact which it endeavours to establish." This formulation implies that the reliability and strength of evidence must be proportionate to the claim's deviation from established natural regularities, as weaker testimony would more plausibly stem from error, deception, or exaggeration than from the event itself occurring.^[8] Prior to Hume, philosophical skepticism toward extraordinary reports existed in ancient sources, such as Cicero's De Divinatione (44 BCE), which questions prophetic dreams and omens based on their inconsistency with observed patterns, though without the explicit probabilistic balancing of testimony against event improbability. Similarly, Sextus Empiricus in Outlines of Pyrrhonism (c. 200 CE) advocates suspending judgment on wonders lacking confirmatory experience, emphasizing empirical uniformity over isolated claims. However, these lack Hume's precise criterion tying evidence quality to claim extraordinariness. Hume's argument draws on empirical induction, prioritizing observed regularities as the baseline for assessing deviations, and has been interpreted as an early probabilistic skepticism where prior experience sets a high bar for anomalous reports. This approach influenced later evidential standards in philosophy of science, though critics like Richard Price in 1767 challenged its dismissal of all miracle testimony by arguing for potential overrides via cumulative evidence.^[9]

Scientific and Skeptical Antecedents

The probabilistic foundations of demanding heightened evidentiary standards for improbable assertions trace to the early 19th century, particularly in the work of French mathematician Pierre-Simon Laplace. In his Essai philosophique sur les probabilités (first published in 1812, with expanded editions thereafter), Laplace emphasized that the credibility of reported facts diminishes as their antecedent improbability increases, requiring testimony or evidence to be proportionally stronger to overcome such priors. He articulated this as: "From this we must generally conclude that the more extraordinary a fact, the more it needs to be supported by strong proofs; for those who report it would undoubtedly have to be more enlightened than the ordinary run of men, more free from error or passion, and more honest, to guarantee such a fact."^[2] This formulation integrated empirical observation with mathematical probability, influencing scientific assessments of anomalous claims by weighting evidence against established natural laws.^[4] In practice, 19th-century scientific investigations of purported supernatural phenomena operationalized similar standards, prioritizing controlled experimentation over unverified reports. For instance, physicist Michael Faraday's 1853 inquiry into spiritualist "table-turning" sessions concluded that movements attributed to ethereal forces resulted from ideomotor responses—unconscious muscular actions by participants—after devising apparatuses to detect and isolate such effects, thereby nullifying claims lacking mechanical verifiability. Such empirical scrutiny, echoed in later exposés like those by magician Harry Houdini in the 1920s against fraudulent mediums, underscored skepticism's reliance on falsifiable demonstrations rather than probabilistic accommodations for rarity alone. These efforts prefigured modern scientific skepticism's institutionalization, where low-probability assertions, such as extrasensory perception or perpetual motion, faced demands for replicable data exceeding ordinary thresholds. By the mid-20th century, formalized skeptical discourse explicitly invoked evidentiary proportionality. Sociologist Marcello Truzzi, co-founder of the Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP, established 1976), stated in 1978: "Extraordinary claims require extraordinary proof." Truzzi's zetetic approach—advocating provisional agnosticism pending rigorous testing—bridged probabilistic reasoning with organized inquiry into fringe claims, influencing the nascent movement's methodological rigor amid rising pseudoscientific assertions post-World War II.^[2] This pre-Sagan articulation aligned with broader skeptical literature, such as Martin Gardner's 1957 critique Fads and Fallacies in the Name of Science, which dissected unsubstantiated hypotheses through evidential inadequacy rather than outright dismissal.

Carl Sagan's Popularization

Astronomer and science communicator Carl Sagan prominently featured the principle that "extraordinary claims require extraordinary evidence" in the twelfth episode of his 1980 television series Cosmos: A Personal Voyage, titled "Encyclopaedia Galactica," which aired on December 14, 1980.^[10] In this episode, Sagan invoked the adage while discussing the search for extraterrestrial intelligence (SETI) and evaluating reports of unidentified flying objects (UFOs), emphasizing that claims of alien visitations lacked the robust supporting data needed to overturn established scientific understanding, such as the vast distances between stars and the absence of verifiable artifacts.^[11] He contrasted anecdotal eyewitness accounts with the rigorous standards of empirical verification, arguing that unconfirmed sightings since 1947 failed to meet the threshold for acceptance.^[10] Sagan reiterated and expanded upon the principle in his 1995 book The Demon-Haunted World: Science as a Candle in the Dark, where it served as a cornerstone of his advocacy for scientific skepticism against pseudoscientific and supernatural assertions, including alien abductions, faith healing, and demonic possessions.^[12] In the text, he positioned the requirement for proportional evidence as essential to distinguishing valid scientific inquiry from credulity, drawing on historical examples of debunked phenomena like Martian canals to illustrate how insufficient evidence perpetuates unfounded beliefs.^[13] The book, published amid growing public interest in paranormal topics during the late 20th century, urged readers to demand empirical rigor, particularly in media and policy contexts prone to sensationalism.^[1] Through Cosmos, which reached an estimated 500 million viewers worldwide, and The Demon-Haunted World, Sagan elevated the aphorism—sometimes termed the "Sagan standard"—from philosophical antecedent to a widely recognized heuristic in skeptical and scientific discourse.^[14] His formulation, while echoing earlier ideas from figures like Pierre-Simon Laplace, gained traction due to Sagan's accessible style and authority as a planetary scientist involved in projects like Voyager and Viking, fostering its adoption in debunking extraordinary assertions lacking commensurate proof.^[4] This popularization underscored a commitment to evidence scaled to claim improbability, influencing subsequent applications in evaluating fringe theories.^[15]

Epistemological Foundations

Bayesian Framework and Prior Probabilities

The Bayesian framework provides a probabilistic model for evaluating the principle that extraordinary claims require correspondingly strong evidence, emphasizing the role of prior probabilities in belief updating. Bayes' theorem formalizes this as the posterior probability P(H|E) = \frac{P(E|H) P(H)}{P(E)}, where H is the hypothesis, E is the evidence, P(H) is the prior probability of H, P(E|H) is the likelihood of observing E if H is true, and P(E) normalizes over all possibilities. In this setup, hypotheses with low priors—such as those positing rare or unprecedented phenomena—demand evidence yielding a high likelihood ratio \frac{P(E|H)}{P(E|\neg H)} to achieve a credibly high posterior probability, as the denominator P(E) incorporates the prior improbability.^[4]^[6] Prior probabilities represent the initial degree of belief in a hypothesis before considering new evidence, derived from background knowledge, empirical frequencies, or theoretical considerations. For extraordinary claims, which challenge well-established scientific consensus (e.g., violations of conservation laws or undocumented biological mechanisms), priors are typically assigned very low values because historical data shows such events occur infrequently or not at all under controlled conditions. This assignment is not arbitrary but grounded in the cumulative evidence favoring simpler, more probable alternatives, ensuring that priors reflect the causal structure of observed reality rather than unsubstantiated speculation. For instance, claims of paranormal perception have been assigned priors near zero in Bayesian analyses due to repeated failures in replication across rigorous experiments.^[6]^[4] The evidential threshold thus scales with prior improbability: ordinary claims, with priors near 0.5 or higher based on routine reproducibility, update posteriors readily with modest evidence, whereas extraordinary ones require "extraordinary" evidence—often multiple independent confirmations or data defying null expectations—to shift beliefs meaningfully. Bayesian meta-analyses of specific extraordinary claims, such as non-local perception, illustrate this by computing Bayes factors that weigh evidence against low priors, frequently finding insufficient support despite initial positive results. Critics within Bayesian epistemology note that priors can introduce subjectivity, but rigorous methods constrain them through intersubjective agreement on background data, preventing undue skepticism or credulity. This framework underscores the principle's compatibility with empirical prioritization, where evidence must proportionally counter the claim's inherent implausibility to justify acceptance.^[4]

Links to Falsifiability and Occam's Razor

Falsifiability, as proposed by Karl Popper in his 1934 work Logik der Forschung, stipulates that for a theory to be scientific, it must be possible in principle to conceive of observations that would refute it.^[16] This criterion complements the requirement for extraordinary evidence by ensuring that bold assertions are not only testable but also subjected to rigorous scrutiny proportional to their deviation from prior knowledge; mere potential refutability without substantial supporting data risks perpetuating unverified speculations, as single confirming instances cannot conclusively validate universal or improbable claims against the asymmetry of induction.^[17] In Carl Sagan's baloney detection toolkit, falsifiability and the extraordinary evidence standard operate in tandem: the former filters out inherently untestable propositions, while the latter demands evidential robustness for those that pass initial testability, preventing acceptance based on anecdotal or weakly corroborated data that might mimic confirmation but fail under repeated falsification attempts.^[18] Occam's razor, attributed to William of Ockham (c. 1287–1347), posits that among competing hypotheses consistent with the data, the one invoking the fewest unproven assumptions should be preferred.^[19] Extraordinary claims frequently entail additional entities, mechanisms, or low-probability events, rendering them less parsimonious; thus, the evidence threshold elevates to offset this added complexity, enforcing razor-like economy by requiring claimants to demonstrate that simpler alternatives are inadequate before adopting costlier explanatory frameworks.^[20] This integration underscores a unified epistemological strategy where parsimony guides prior skepticism, amplified for outlier claims to prioritize causal efficiency over speculative elaboration.^[17]

Causal Realism and Empirical Prioritization

Causal realism maintains that causation constitutes a fundamental aspect of reality, involving objective processes and structures that generate effects, irreducible to patterns of correlation or probabilistic regularities alone. This perspective contrasts with reductionist views that treat causation as mere constant conjunction of events, as critiqued in Humean empiricism, by insisting on the existence of underlying mechanisms that can be investigated and confirmed through targeted inquiry.^[21]^[22] In the evaluation of claims, particularly those diverging from established causal frameworks—such as assertions of telepathy or perpetual motion devices—causal realism requires proponents to delineate and substantiate the specific mechanisms purportedly at work, ensuring consistency with broader scientific understanding rather than positing ad hoc violations without demonstrable pathways. Failure to identify such mechanisms renders the claim vulnerable to dismissal, as empirical correlations, even if statistically significant, do not suffice without evidence of generative processes linking antecedents to outcomes.^[23]^[24] The principle of extraordinary claims requiring extraordinary evidence aligns with causal realism by elevating the standard for validating novel causal posits, which inherently challenge entrenched knowledge derived from millennia of observation and experimentation. For instance, claims implying acausal influences or mechanisms defying conservation principles demand not only replicable outcomes but also rigorous dissection of the intervening processes, often through controlled interventions that isolate variables and rule out confounders.^[25] This approach mitigates errors arising from illusory causations, such as those stemming from selection bias or post hoc rationalizations, which proliferate in uncontrolled settings. Peer-reviewed analyses emphasize that without mechanistic evidence, even large datasets may reflect artifacts rather than true causality, underscoring the principle's role in safeguarding against overinterpretation of preliminary findings.^[26] Empirical prioritization complements causal realism by mandating that evidentiary assessment favor data from systematic, falsifiable tests over subjective reports or theoretical speculation, thereby anchoring belief formation in verifiable phenomena. In skeptical inquiry, this entails demanding high-quality empirical support—such as randomized controlled trials or longitudinal observations—for extraordinary assertions, where baseline priors derived from historical failures of similar claims (e.g., over 99% of paranormal investigations yielding null results in controlled conditions) necessitate evidence robust enough to overturn accumulated counter-evidence.^[1] Sources advancing weak empiricism, including anecdotal compilations from biased institutional reviews, often inflate claim credibility through confirmation-seeking designs, a flaw causal realism exposes by requiring mechanism-tracing that such data rarely provide.^[27] Thus, the principle enforces a hierarchy where empirical demonstrations of causality, reproducible across independent labs, supersede interpretive narratives, fostering reliability in knowledge claims amid pervasive risks of Type I errors in fringe domains.^[28]

Applications and Examples

In Pseudoscience and Paranormal Claims

The principle that extraordinary claims require extraordinary evidence is frequently invoked in evaluating pseudoscientific and paranormal assertions, such as extrasensory perception (ESP), ghost manifestations, or homeopathic remedies that purportedly act despite dilutions exceeding Avogadro's number, rendering them chemically indistinguishable from water.^[29] These claims typically challenge foundational scientific paradigms like conservation of energy, causality, or biochemical mechanisms, demanding replicable experiments, statistical rigor, and elimination of confounds like sensory leakage or expectation bias rather than reliance on personal testimonies or inconsistent observations.^[30] In parapsychology, investigations into psi phenomena—encompassing telepathy, clairvoyance, and precognition—have produced meta-analyses reporting small positive effect sizes, yet these are undermined by failures in independent replications, evidence of questionable research practices, and Bayesian reassessments favoring the null hypothesis.^[31] ^[32] For example, a meta-analysis of 90 precognition experiments yielded a modest effect, but subsequent critiques highlighted selective reporting and non-replicability, aligning with broader concerns over p-hacking and publication bias in psi research.^[33] The James Randi Educational Foundation's One Million Dollar Challenge, active from 1996 to 2015, tested numerous paranormal claimants under controlled protocols but awarded the prize to none, underscoring the absence of verifiable demonstrations despite incentives.^[34] Pseudoscientific therapies like homeopathy exemplify the principle's utility, positing "memory" in diluted solutions without molecular traces, a mechanism unsupported by quantum or material evidence. Systematic reviews, including those by the Australian National Health and Medical Research Council, conclude that homeopathic treatments show no effects beyond placebo across diverse conditions, with high-quality trials consistently null.^[35] This evidentiary shortfall persists despite anecdotal endorsements, reinforcing skepticism toward claims diverging from dose-response pharmacology and randomized controlled trial standards.^[36] Applications extend to paranormal entities, such as UFO encounters or spectral apparitions, where initial reports demand physical artifacts, radar data, or physiological correlates to override prosaic explanations like misidentification or hoaxes; historical patterns reveal most dissolve under scrutiny without yielding paradigm-shifting proof.^[29] Overall, the principle serves as a evidentiary filter, privileging claims substantiated by convergent, falsifiable data over those sustained by confirmatory bias or institutional resistance to null findings in fringe domains.

In Scientific Discovery and Hypothesis Testing

In hypothesis testing, the principle manifests as a heightened evidentiary threshold for alternative hypotheses that deviate markedly from established knowledge or ordinary expectations, aligning with the statistical convention of assuming the null hypothesis unless compelling data warrant rejection. The burden of proof rests with proponents of the alternative, requiring evidence not merely consistent with the claim but sufficiently robust to overcome the presumption of the null, often quantified via p-values or likelihood ratios. For routine claims, a standard significance level like p < 0.05 suffices, but extraordinary hypotheses—those implying paradigm shifts or rare phenomena—demand stricter criteria to minimize false positives, such as multiple replications or elevated confidence intervals. This approach mitigates confirmation bias and ensures causal inferences rest on empirical patterns rather than anomalies./09:_Hypothesis_Testing_with_One_Sample/9.04:_Distribution_Needed_for_Hypothesis_Testing) Particle physics exemplifies this in discovery protocols, where claims of new fundamental particles necessitate a five-sigma (5σ) significance level, equivalent to a false positive rate below 1 in 3.5 million under the null. This convention, formalized since the 1970s to address multiple testing and "look-elsewhere" effects in high-dimensional data, reflects the extraordinary nature of upending the Standard Model. The Higgs boson's detection at CERN's Large Hadron Collider in 2012, combining ATLAS and CMS results at ~5σ after extensive cross-verification, met this bar following years of data accumulation exceeding prior null predictions of non-existence. Subsequent analyses confirmed compatibility with theoretical expectations, culminating in the 2013 Nobel Prize, whereas lesser signals (e.g., 3σ "bumps") are deemed mere evidence, not discovery.^[37]^[38]^[39] Bayesian methods further operationalize the principle by assigning low prior probabilities to extraordinary claims, such as novel physical laws or undetected mechanisms, thereby requiring disproportionately strong likelihoods from data to yield high posterior credibility. In fields like epidemiology or cosmology, this tempers enthusiasm for outliers; for instance, gravitational wave detections by LIGO in 2015 demanded Bayesian factors corroborating signal over noise across detectors, rejecting instrumental artifacts as ordinary explanations. Such frameworks prioritize causal realism, favoring hypotheses with mechanistic plausibility over those reliant on improbable coincidences, though they invite scrutiny of prior elicitation to avoid subjective conservatism. Peer-reviewed validations, including independent reproductions, thus serve as the "extraordinary evidence" distinguishing validated discoveries from provisional conjectures.^[40]^[41]

Broader Uses in Policy and Public Discourse

In public policy formulation, the principle serves as a heuristic for demanding proportionately strong empirical support for assertions that propose sweeping regulatory, fiscal, or behavioral interventions, particularly when they impose significant economic burdens or alter entrenched practices. For example, in nutrition science informing government dietary guidelines, advocates have urged adherence to the standard for claims about macronutrient-specific diets reversing obesity epidemics, emphasizing the need for randomized controlled trials with long-term outcomes over observational correlations, given the trillions in projected healthcare costs tied to such policies.^[42] This approach counters premature endorsement of unverified mechanisms, as seen in historical shifts like the U.S. Dietary Guidelines' emphasis on low-fat regimens, which later faced criticism for lacking causal rigor despite widespread adoption.^[42] The maxim also permeates public discourse on electoral integrity and governance reforms, where allegations of extraordinary institutional failures—such as coordinated fraud altering national election outcomes—must substantiate with comprehensive audits, chain-of-custody validations, and statistical anomaly resolutions rather than disparate affidavits. In the context of the 2020 U.S. presidential election, skeptics applied the principle to dismiss unsubstantiated theories of mass manipulation, arguing that upending certified results in swing states required forensic-level proof absent from post-election litigation, which courts uniformly rejected for evidentiary insufficiency across over 60 cases by mid-2021.^[43] National security policy debates further illustrate its utility, as in evaluating intelligence claims justifying surveillance expansions or military engagements; Edward Snowden's 2013 disclosures on NSA programs were defended as meeting the threshold through verifiable documents revealing bulk data collection on U.S. citizens, prompting reforms like the USA Freedom Act of 2015 amid congressional hearings that validated the scale of overreach.^[44] Conversely, policy responses to unidentified aerial phenomena (UAP) have sparked contention, with proponents of increased funding arguing that preliminary Pentagon reports from 2021—documenting 144 unexplained incidents—warrant investigation without dogmatic dismissal, though critics maintain that paradigm-shifting conclusions on non-human origins demand multimodal corroboration beyond sensor data.^[45]

Criticisms and Counterarguments

Subjectivity and Definitional Issues

Critics contend that the principle's core terms—"extraordinary claims" and "extraordinary evidence"—lack objective definitions, rendering their application subjective and prone to inconsistent interpretation.^[14] A claim is deemed "extraordinary" if it conflicts with established empirical knowledge or possesses a low prior probability, yet the selection of that background knowledge depends on the evaluator's worldview, potentially embedding cultural, institutional, or personal biases.^[1] For instance, academic consensus, often shaped by prevailing paradigms, may classify certain hypotheses as extraordinary while overlooking anomalies that challenge those paradigms, as seen in historical shifts like the acceptance of plate tectonics, which initially faced dismissal despite accumulating geological data.^[46] This subjectivity extends to priors in Bayesian frameworks, where "extraordinary" status hinges on assigning numerical probabilities to hypotheses; such assignments require judgments informed by incomplete data, leading to disputes over whether a claim's improbability is inherent or merely reflective of current evidential gaps.^[47] Philosophers note that without standardized criteria, evaluators risk conflating low priors with outright impossibility, a form of definitional overreach that Hume's proportionality rule—belief scaled to evidence strength—avoids by not imposing a qualitative threshold.^[1] Definitional ambiguity further arises in specifying "extraordinary evidence," often described as requiring multiple independent lines of confirmation, high statistical power, or mechanistic explanations, yet these standards remain elastic and context-dependent.^[14] In practice, what qualifies as sufficient to elevate a low-prior claim—such as replication across labs or consilience with theory—varies, with skeptics sometimes demanding evidence exceeding ordinary thresholds without quantifying the increment needed.^[47] This vagueness can foster gatekeeping, where sources with systemic biases, such as those in mainstream scientific institutions, undervalue evidence for paradigm-threatening claims, as critiqued in analyses of pseudoscience dismissals that prioritize consensus over raw evidential weight.^[46] Proponents counter that rigorous application mitigates subjectivity by anchoring definitions in reproducible empirical tests, but detractors argue the principle's informal phrasing invites arbitrary enforcement over falsifiable standards.^[1]

Claims of Equivalence to Ordinary Evidence Standards

Critics maintain that the evidential bar for extraordinary claims aligns with ordinary standards, emphasizing uniform criteria such as empirical reliability, independent corroboration, and consistency with established knowledge, rather than imposing a distinct, heightened threshold. They argue that the phrase "extraordinary evidence" ambiguously elevates the requirement beyond methodological norms, potentially fostering undue skepticism toward novel hypotheses that could advance understanding, as seen in historical scientific breakthroughs where initial counterintuitive propositions succeeded on the strength of convergent ordinary data.^[46]^[48] In philosophical critiques of related maxims, such as David Hume's contention that testimony for miracles must render their falsehood more improbable than the event itself, scholars like John Earman demonstrate that such standards collapse under probabilistic scrutiny, failing to justify dismissing reliable attestation outright. Earman's analysis, published in 2000, reconstructs Hume's argument as logically deficient, showing that ordinary testimonial evidence—evaluated for factors like witness multiplicity and absence of collusion—can rationally support improbable events without necessitating impossibly robust proof.^[49]^[50] Proponents of equivalence further invoke abductive reasoning, where hypotheses are selected as the best explanation of data; here, an extraordinary claim merits endorsement if it outperforms alternatives using standard evidential metrics, irrespective of its deviation from priors. Philosopher Theodore Schick exemplifies this view, asserting that extraordinary claims need not demand extraordinary evidence when they furnish the superior accounting for observations, as articulated in his contributions to pseudoscience critiques.^[51] From a Bayesian standpoint, while low priors demand evidence yielding a substantial likelihood ratio to elevate posterior credence, the admissible forms—direct observations, controlled replications, or inferential patterns—remain qualitatively identical to those for mundane claims, with "extraordinariness" addressed through evidential volume or precision rather than a redefined standard. This perspective counters the dictum's implication of categorical disparity, positing instead that uniform application prevents arbitrary dismissal of paradigm-shifting propositions.^[1]^[46]

Potential for Bias in Prior Assignments

The assignment of low prior probabilities to extraordinary claims under the principle is vulnerable to subjectivity, as judgments of what qualifies as "extraordinary" depend on an evaluator's existing knowledge, cultural background, and cognitive biases rather than objective metrics.^[52] This subjectivity arises because priors in Bayesian inference reflect personal or collective beliefs about baseline likelihoods, which can embed unexamined assumptions favoring established paradigms over novel ones.^[53] Critics argue that such priors often conflate empirical improbability with ideological discomfort, leading to systematically undervalued hypotheses that challenge dominant narratives.^[52] Institutional environments, including academia and scientific peer review, amplify this potential for bias through mechanisms like status signaling and conformity pressures, where claims from low-prestige sources or dissenting viewpoints receive disproportionately low priors irrespective of evidential merit.^[54] For instance, a 2025 audit of large language model simulations of peer review found consistent institutional-prestige bias, with identical papers attributed to lower-status affiliations facing rejection rates up to 20% higher, suggesting analogous dynamics in human evaluators' prior assignments.^[54] Systemic ideological homogeneity in these institutions—evidenced by surveys showing over 90% left-leaning faculty in social sciences at top U.S. universities as of 2020—further skews priors against claims contradicting progressive orthodoxies, such as those questioning anthropogenic climate dominance or biological sex dimorphisms. Historical precedents illustrate how biased priors delayed validation of ultimately correct extraordinary claims. Alfred Wegener's 1912 proposal of continental drift was dismissed as implausible for decades, with geologists assigning near-zero priors due to its conflict with the prevailing theory of rigid, fixed continents, despite accumulating geological and fossil evidence; acceptance only followed mid-20th-century seafloor spreading data confirming plate tectonics. Similarly, Ignaz Semmelweis's 1847 advocacy for handwashing to prevent puerperal fever was rejected by the medical establishment, which afforded low priors to the germ transmission mechanism amid prevailing miasma theory biases, contributing to thousands of preventable deaths until Pasteur and Lister's work shifted paradigms in the 1860s-1880s. These cases demonstrate how entrenchment in status quo priors can equate to confirmation bias, where evaluators demand "extraordinary" evidence thresholds calibrated to preserve existing beliefs rather than neutrally assess likelihoods.^[55] In policy and public discourse, such biases manifest when media or regulatory bodies apply uneven prior standards; for example, early dismissals of the COVID-19 lab-leak hypothesis as a "conspiracy theory" in 2020 reflected low priors influenced by geopolitical sensitivities and institutional deference to certain expertise, despite FBI assessments by 2023 deeming it the most likely origin based on intelligence analysis. This pattern underscores the risk that the principle, when misapplied through biased priors, entrenches dogmas under the guise of skepticism, potentially stifling causal inquiry into underrepresented hypotheses.^[56] To mitigate this, proponents advocate explicit prior elicitation and sensitivity analyses in Bayesian frameworks, testing conclusions across a range of plausible priors to expose subjective influences.^[57]

Empirical Evaluations and Case Studies

Historical Case Studies of Claim Validation

The validation of Albert Einstein's general theory of relativity in 1915 required evidence surpassing Newtonian predictions, particularly the claim that the Sun's gravity would deflect starlight by 1.75 arcseconds—double the Newtonian value of 0.87 arcseconds. British expeditions led by Arthur Eddington observed the total solar eclipse of May 29, 1919, from Príncipe in the Gulf of Guinea and Sobral in Brazil, photographing stars near the eclipsed Sun to measure positional shifts. Analysis yielded deflections of 1.98 ± 0.11 arcseconds at Príncipe and 1.75 ± 0.13 arcseconds at Sobral, aligning with relativity while contradicting Newtonian mechanics. These results, presented to the Royal Society and Royal Astronomical Society on November 6, 1919, provided decisive empirical confirmation, shifting scientific consensus despite initial skepticism toward the radical spacetime curvature concept.^[58]^[59] Similarly, the 1840s discrepancies in Uranus's orbit—discovered by William Herschel in 1781 and refined by Johann Bode's observations—posed an extraordinary challenge to Newtonian gravity, implying an unseen massive body causing perturbations. French mathematician Urbain Le Verrier applied perturbation calculations to predict the perturbing planet's position at roughly 12 hours right ascension and 14 arcminutes south declination, relaying coordinates to Johann Galle at Berlin Observatory on September 18, 1846. Galle's telescope search on September 23, 1846, identified Neptune within 1° of the forecast, with subsequent tracking confirming its orbital influence on Uranus. English astronomer John Couch Adams had independently derived a proximate position earlier that year, underscoring the claim's robustness through replicable mathematics rather than direct sighting. This discovery affirmed gravitational theory's predictive accuracy against alternatives like revised Uranus mass estimates.^[60] Alfred Wegener's 1912 continental drift hypothesis claimed continents were once conjoined in a supercontinent (Pangaea) and had separated over 200 million years, evidenced by jigsaw-fit coastlines, matching fossils (e.g., Mesosaurus across South America and Africa), and identical rock strata (e.g., Appalachian-Caledonian mountains). Dismissed until the mid-20th century for lacking a driving mechanism, validation accelerated with Harry Hess's 1960 seafloor spreading model, positing new oceanic crust formation at mid-ocean ridges via upwelling mantle material. Vine and Matthews's 1963 analysis of magnetic striping—alternating normal and reversed polarity bands symmetric around ridges, dated via radiometric methods to match geomagnetic reversals—demonstrated crust aged progressively from ridges, reaching 180 million years at trenches. Earthquake and volcanic alignments along plate boundaries, quantified by 1960s seismology, further corroborated rigid plate motions at 1-10 cm/year, solidifying plate tectonics by 1967-1968 conferences.^[61]^[62] These cases highlight how claims overturning entrenched models—geocentric intuition, planetary isolation, or fixed continents—demanded multifaceted, predictive evidence, including precise astronomical measurements, mathematical forecasts, and geophysical mappings, to achieve paradigm shifts without reliance on mere correlation.

Modern Debates in Controversial Fields

In the debate over unidentified anomalous phenomena (UAP), formerly known as UFOs, congressional hearings in July 2023 featured testimony from retired intelligence official David Grusch alleging that the U.S. government possesses non-human craft and biologics recovered from crash sites, based on second-hand accounts from over 40 witnesses.^[63] Critics invoked the principle that such assertions of extraterrestrial technology demand rigorous, physical evidence beyond anecdotal reports, as emphasized by NASA's 2023 independent study which found no empirical support for extraterrestrial origins despite analyzing over 800 cases. The Pentagon's All-domain Anomaly Resolution Office similarly reported in 2024 that while some UAP exhibit anomalous flight characteristics, claims of recovered non-human materials lack verifiable data, highlighting how institutional secrecy and classified evidence complicate public scrutiny without compromising scientific standards.^[64] Regarding the origins of SARS-CoV-2, the lab-leak hypothesis—positing an accidental release from the Wuhan Institute of Virology—was initially marginalized as a fringe theory by much of the scientific establishment and media in 2020, despite the institute's documented gain-of-function research on coronaviruses funded in part by U.S. agencies like the National Institutes of Health.^[65] By 2023, however, the FBI assessed with moderate confidence that the virus most likely emerged from a lab incident, while the Department of Energy reached a similar conclusion with low confidence, based on genomic features like the furin cleavage site uncommon in natural sarbecoviruses and the absence of a proximal wildlife reservoir after extensive searches.^[66] Proponents of the principle argued that the natural zoonosis claim, while ordinary, required its own evidentiary support, which remained indirect (e.g., relying on historical precedents like SARS-1), whereas the lab-leak's accumulation of circumstantial data— including the institute's biosafety lapses reported in 2018 U.S. diplomatic cables—gradually met thresholds for plausibility without constituting definitive proof.^[67] This case illustrated tensions where prior probabilities (proximity to a high-risk lab) clashed with institutional biases, as emails from 2020 revealed virologists privately acknowledging lab-leak plausibility before publicly endorsing natural origins in The Lancet.^[65] In treatments for gender dysphoria among youth, advocates have claimed that interventions like puberty blockers and cross-sex hormones substantially reduce suicide risk and enable long-term psychological well-being, positioning these as evidence-based necessities despite their irreversible effects.^[68] The 2024 Cass Review, commissioned by the UK's National Health Service, evaluated over 100 studies and concluded that the evidence base for these claims is of low quality, lacking randomized controlled trials and showing weak correlations between medical transition and improved mental health outcomes, with desistance rates in untreated youth historically exceeding 80% by adulthood. Applying the principle, skeptics contended that assertions of net benefits—contradicting prior understandings of dysphoria's developmental fluidity—necessitate high-quality longitudinal data, particularly given European shifts: Sweden's national board restricted blockers to research settings in 2022 citing uncertain benefits and risks like infertility, while Finland's guidelines in 2020 prioritized psychotherapy over medicalization for most adolescents.^[69] These debates underscore how reliance on observational studies and self-reported improvements, amid advocacy-driven research, has prompted calls for Bayesian reassessment of priors favoring caution in irreversible interventions.^[70]

Lessons from Failed or Confirmed Extraordinary Claims

The 1989 announcement of cold fusion by chemists Stanley Pons and Martin Fleischmann represented an extraordinary claim of achieving nuclear fusion at room temperature using electrolysis of heavy water on palladium electrodes, promising unlimited clean energy without the extreme conditions required by conventional fusion.^[71] Initial reports of excess heat and neutron emissions generated widespread excitement, but subsequent attempts by dozens of laboratories, including those at MIT and Caltech, failed to reproducibly detect the predicted fusion signatures under controlled conditions.^[72] The lack of precise methodology details, inconsistent results, and absence of verifiable nuclear byproducts highlighted insufficient evidentiary rigor, leading to the claim's rejection by the scientific community within months; this case underscores that extraordinary claims demand replicable experiments with robust controls to distinguish genuine phenomena from artifacts of experimental error or wishful interpretation.^[72] Similarly, the 1903 discovery of N-rays by Prosper-René Blondlot involved claims of a new form of radiation detectable by human vision in darkened rooms, an extraordinary assertion challenging established physics.^[72] Dozens of French scientists initially confirmed the effect, but American physicist Robert W. Wood's intervention—removing a key prism from the apparatus without Blondlot's knowledge, yet the "detection" persisted—exposed it as a product of expectation bias and sensory illusion, with no objective measurements or independent verification.^[72] This "pathological science" episode illustrates the necessity for blinded protocols and quantitative instrumentation in evaluating extraordinary claims, as subjective confirmations can propagate errors until falsified by stringent testing. In contrast, the 2012 confirmation of the Higgs boson at CERN's Large Hadron Collider validated a long-predicted particle essential for explaining particle masses within the Standard Model, an extraordinary theoretical requirement proposed by Peter Higgs and others in 1964. The ATLAS and CMS collaborations amassed over 10^15 proton-proton collisions, yielding a 5-sigma statistical significance (probability of false positive less than 1 in 3.5 million) through precise decay product analyses, overcoming initial skepticism with data from multiple independent channels. This success demonstrates that extraordinary claims can be upheld when supported by vast, high-precision datasets and peer-reviewed scrutiny, enabling integration into established frameworks without undermining them. Another confirmed case is the 1919 solar eclipse expedition led by Arthur Eddington, which provided empirical evidence for Albert Einstein's general theory of relativity by measuring starlight deflection matching the predicted 1.75 arcseconds—twice the Newtonian value—during totality. Subsequent validations, including gravitational redshift observations in 1925 and modern GPS corrections accounting for relativistic effects (up to 38 microseconds daily), have accumulated to extraordinary evidentiary weight, transforming relativity from a bold hypothesis into foundational physics. These instances reveal that while low prior probabilities necessitate elevated evidence thresholds, consistent, multifaceted corroboration across experiments and predictions can compel acceptance, fostering scientific advancement. Key lessons from these cases include the critical role of reproducibility and falsifiability in weeding out unsubstantiated claims, as failures like cold fusion diverted resources equivalent to millions in rushed replications before debunking.^[71] Confirmed examples affirm that extraordinary evidence—quantitative, independently verifiable, and predictive—elevates improbable ideas to consensus, emphasizing Bayesian-like updating where evidence strength must countervail priors informed by physical laws.^[14] Moreover, premature publicity without exhaustive validation, as in N-rays, amplifies biases, whereas methodical accumulation, as with the Higgs, mitigates them, ensuring claims withstand adversarial testing rather than anecdotal support.^[72]

References

[1]
Do Extraordinary Claims Require Extraordinary Evidence? - PMC
Oct 20, 2016 · In 1979 astronomer Carl Sagan popularized the aphorism “extraordinary claims require extraordinary evidence” (ECREE).
[2]
Quote Origin: Extraordinary Claims Require Extraordinary Evidence
Dec 5, 2021 · Here are two versions of a pertinent adage: Extraordinary claims require extraordinary evidence. Extraordinary claims require extraordinary ...
[3]
Of Miracles - Hume Texts Online
He therefore concluded, like a just reasoner, that such an evidence carried falsehood upon the very face of it, and that a miracle, supported by any human ...
[4]
Pierre-Simon Laplace - Wikipedia
Most often repeated as "The weight of evidence for an extraordinary claim must be proportioned to its strangeness." (see also: Sagan standard). This ...Early years · Analytic theory of probabilities · Laplace's demon · Laplace transforms
[5]
Extraordinary Claims Require Extraordinary Evidence - NIH
“Extraordinary claims require extraordinary evidence” was a phrase made popular by Carl Sagan who reworded Laplace's principle, which says that “the weight ...
[6]
6.3: Probability and Belief - Bayesian Reasoning
Mar 7, 2024 · ... Extraordinary claims require extraordinary evidence.” Putting this in terms of personal probabilities, an implausible hypothesis—and ...
[7]
Prior Probability: the Dirty Little Secret of “Evidence-Based ...
Feb 22, 2008 · So the probability of both conditions being true is less than the probability of either one being true. Extraordinary claims require ...
[8]
Do Extraordinary Claims Require Extraordinary Evidence ...
Nov 13, 2020 · In this article, I will argue that the dictum that extraordinary claims require extraordinary evidence, and the philosophy of David Hume that it encapsulates, ...
[9]
An Enquiry Concerning Human Understanding - Project Gutenberg
Enquiries concerning the human understanding, and concerning the principles of morals, by David Hume.
[10]
Has David Hume shown that it can never be reasonable to believe ...
In sum, Hume's argument against believing testimony of miracles is built on the idea that miracles, by definition, are events that deviate from an otherwise ...
[11]
Encyclopædia Galactica - Carl Sagan and Ann Druyan
Cosmos, Episode 12. December 14, 1980 ... Extraordinary claims require extraordinary evidence. 01:32. Since 1947, there have been hundreds of thousands of ...
[12]
Exploring Carl Sagan's Cosmos: Episode 12, "Encyclopaedia ...
Feb 1, 2013 · Extraordinary claims require extraordinary evidence.” This is the major point Sagan makes in his discussion of extraterrestrial life, ...
[13]
Carl Sagan Quotes About Evidence
“Demon-Haunted World: Science as a Candle in the Dark”, p.314, Ballantine ... Extraordinary claims require extraordinary evidence. Carl Sagan · Believe ...
[14]
Carl Sagan's THE DEMON-HAUNTED WORLD: Science As a ...
Jan 31, 2020 · But after the canals were debunked, stories of visits by Martians disappeared…. Ch7, The Demon-Haunted World. Belief in demons was widespread in ...<|separator|>
[15]
The Sagan Standard: Extraordinary Claims Require ... - Effectiviology
The Sagan standard is the adage that “extraordinary claims require extraordinary evidence” (a concept abbreviated as ECREE).
[16]
Extraordinary Claims Require Extraordinary Evidence—The Carl ...
Nov 9, 2018 · In the penultimate episode of Cosmos, Sagan states that 'extraordinary claims require extraordinary evidence' in a phrase that has come to ...
[17]
Karl Popper: Falsification Theory - Simply Psychology
Jul 31, 2023 · Karl Popper's theory of falsification contends that scientific inquiry should aim not to verify hypotheses but to rigorously test and identify conditions under ...
[18]
Carl Sagan's Baloney Detection Kit | Center for Inquiry
Propositions that are untestable, unfalsifiable are not worth much. ... This impatience with ambiguity can be criticized in the phrase: absence of evidence is not ...Missing: extraordinary | Show results with:extraordinary
[19]
[PDF] The Fine Art of Baloney Detection
Carl Sagan. The human understanding is no dry light, but receives an infusion ... Like all tools, the baloney detection kit can be misused, applied out ...Missing: extraordinary | Show results with:extraordinary
[20]
Occam's razor: the forgotten key to science literacy - Big Think
Jul 17, 2023 · Already in 2023, many extraordinary claims can be shaved away by Occam's razor. cosmological coupling. The different samples of elliptical ...
[21]
Do extraordinary claims require extraordinary evidence?
Do extraordinary claims require extraordinary evidence? John ... If, however, ECREE is used as a general, guiding rule (in a similar way to Occam's Razor) ...
[22]
(PDF) Causal Realism - ResearchGate
Causal realism is the view that causation is a real and fundamental feature of the world. That is to say, causation cannot be reduced to other features of the ...
[23]
Theories of Explanation | Internet Encyclopedia of Philosophy
Salmon defends his causal realism by rejecting the Humean conception of causation as linked chains of events, and by attempting to articulate an ...
[24]
Causal Realism and the Laws of Nature | Philosophy of Science
Jan 1, 2022 · Rather, causal realism allows us to formulate laws of the form 'When a finite number of quite localized things hold at one time, there will be a ...
[25]
Causal Effects Versus Causal Mechanisms: Two Traditions ... - NIH
Apr 22, 2025 · This paper illustrates key distinctions between statistical and mechanistic approaches to causal investigation by describing their contrasting evidentiary ...Missing: extraordinary | Show results with:extraordinary
[26]
Causal Realism and the Limits of Empiricism: Some Unexpected ...
Here I argue that Hegel ably and insightfully defends Newton's causal realism about gravitational force, in part by exposing a fatal equivocation in the ...
[27]
Case study research and causal inference
Dec 1, 2022 · Case studies, through in-depth research on the actors within systems, can generate evidence about how those actors themselves account for causal ...
[28]
How Skepticism (not Cynicism) Can Raise Scientific Standards and ...
“Extraordinary claims require extraordinary evidence.” Commer- cial health and wellness claims, tending to be both extraordinary and supported by little-to ...
[29]
Towards Stronger Causal Claims in Management Research: Causal ...
Dec 3, 2022 · This article addresses widespread concerns about the reliability and strength of many causal claims made in management research.
[30]
The Virtuous Skeptic
... extraordinary claims require extraordinary evidence,” popularized by Carl ... paranormal experiences, ghosts, Bigfoot, and the like—and those ...
[31]
A Life Preserver for Staying Afloat in a Sea of Misinformation
Extraordinary claims require extraordinary evidence. Essentially, the more implausible or unusual the claim, the more evidence that's required to accept it.
[32]
Why Most Research Findings About Psi Are False: The Replicability ...
Sep 17, 2020 · When a psi experiment is set-up, a distinction between two variables or a hypothesis is proposed (true/false). If another experiment uses the ...
[33]
A Bayes factor meta-analysis of recent extrasensory perception ...
Psi phenomena, such as mental telepathy, precognition, and clairvoyance, have garnered much recent attention. We reassess the evidence for psi effects from ...
[34]
Feeling the future: A meta-analysis of 90 experiments on the ...
Oct 30, 2015 · We here report a meta-analysis of 90 experiments from 33 laboratories in 14 countries which yielded an overall effect greater than 6 sigma.
[35]
The Man Who Destroyed Skepticism - Mitch Horowitz - Medium
Mar 22, 2024 · “To date, Randi's million-dollar prize has not been awarded, but according to Chris Carter, author of Parapsychology and the Skeptics, Randi ...
[36]
Homeopathy is not an effective treatment for any health condition ...
Mar 16, 2015 · The review recommended that homeopathy should not be used to treat health conditions that were chronic, serious, or that could become serious.Missing: claims | Show results with:claims
[37]
The Evidence Says – Homeopathy Does Not Work - NeuroLogica Blog
Feb 22, 2016 · The bar is higher for claims that represent a greater dissonance with existing evidence. Extraordinary claims require extraordinary evidence.<|control11|><|separator|>
[38]
Five sigma revisited - CERN Courier
Jul 3, 2023 · Louis Lyons traces the origins of the “five sigma” criterion in particle physics, and asks whether it remains a relevant marker for claiming the discovery of ...
[39]
Five sigma and all that | Science | The Guardian
Sep 15, 2014 · Five sigma (5σ) is a threshold of about a one-in-2 million chance that a result is just noise, required by particle physicists to claim a new ...Missing: rule | Show results with:rule
[40]
Origin of "5$\sigma$" threshold for accepting evidence in particle ...
Jul 3, 2012 · The 5σ threshold originated in the 1960s particle physics work, promoted by a 1968 Rosenfeld article, to account for multiple comparisons.
[41]
Extraordinary claims, extraordinary evidence? A discussion - PMC
One major shortcoming of the “extraordinary claims require extraordinary evidence” approach stems from the subjectivity of the judgment. What looks ...<|separator|>
[42]
(PDF) Do Extraordinary Claims Require Extraordinary Evidence?
In 1979 astronomer Carl Sagan popularized the aphorism “extraordinary claims require extraordinary evidence” (ECREE). But Sagan never defined the term “ ...
[43]
Extraordinary Claims Require Extraordinary Evidence - Cato Unbound
Feb 2, 2017 · Extraordinary Claims Require Extraordinary Evidence ... Yoni Freedhoff says that the public policy debate about nutrition would benefit from a ...
[44]
Election Deniers' Extraordinary Claims - Glenn Loury | Substack
Aug 29, 2023 · ... Extraordinary claims require extraordinary evidence.” A stolen presidential election would indeed be an extraordinary thing, but ...
[45]
Gellman talks about Snowden revelations | FSI
Nov 17, 2014 · “All extraordinary claims require extraordinary evidence – and he ... public policy question on a program that had secretly expanded in ...
[46]
UFOs: Extraordinary evidence requires extraordinary funding - The Hill
Mar 29, 2023 · To argue is one thing, but to repeat Sagan's mantra that “extraordinary claims require extraordinary evidence” (ECREE) without seeking the ...
[47]
Carl Sagan was wrong: ordinary evidence is enough | Sean McMahon
Jan 10, 2023 · “Extraordinary claims require extraordinary evidence” said Carl Sagan; a dictum which asks us to use the scepticism of Hume to dismiss ...
[48]
Is 'Extraordinary Evidence' Unreasonable? - Skeptical Inquirer
We associate “extraordinary claims require extraordinary evidence” with Carl Sagan. But what is sometimes referred to as “the Sagan Standard” has a long ...
[49]
Do Extraordinary Claims Require Extraordinary Evidence?
The maxim “extraordinary claims require extraordinary evidence,” popularized by Carl Sagan, is one of the most frequently cited phrases in public debates ...
[50]
[PDF] Hume's Abject Failure,The Argument Against Miracles
Part I Hume on Miracles. John Earman. Abstract: Part I contains the author's reconstruction and critical evaluation of Hume's argument against miracles.
[51]
Hume's Abject Failure: The Argument Against Miracles - Amazon.com
30-day returnsBy situating Hume's popular argument in the context of the eighteenth-century debate on miracles, Earman shows Hume's argument to be largely unoriginal and ...
[52]
The Skeptic Encyclopedia of Pseudoscience 2 volume set - epdf.pub
... extraordinary claims do not require extraordinary evidence. It can be reasonable to accept an extraordinary claim in the absence of extraordinary evidence ...<|separator|>
[53]
Extraordinary claims, extraordinary evidence? A discussion
Aug 10, 2021 · One major shortcoming of the “extraordinary claims require extraordinary evidence” approach stems from the subjectivity of the judgment.Missing: criticism | Show results with:criticism
[54]
Bayesian epistemology - Stanford Encyclopedia of Philosophy
Jun 13, 2022 · 4.1 Subjective Bayesianism. Subjective Bayesianism is the view that every prior is permitted unless it fails to be coherent (de Finetti 1970 ...<|separator|>
[55]
Prestige over merit: An adapted audit of LLM bias in peer review
Sep 18, 2025 · The audit reveals a strong and consistent institutional-prestige bias: identical papers attributed to low-prestige affiliations face a ...
[56]
Prior beliefs and the interpretation of scientific results - Journals
Dec 20, 2023 · I discuss a hypothetical scenario where researchers publish results that could either support a theory they believe in, or refute that theory.
[57]
Strong Evidence is Common — LessWrong
Mar 13, 2021 · Running through Bayes' Rule explicitly might produce a bias towards middling values. Extraordinary claims require extraordinary evidence ...
[58]
Subjectivity and objectivity in Bayesian statistics - Project Euclid
However, a scientist cannot simply claim to be correct. The difference is why a scientific Bayes analysis with limited data needs to be fully Bayesian, ...Missing: extraordinary | Show results with:extraordinary
[59]
Observing general relativity | Royal Society
Aug 6, 2024 · The 1919 solar eclipse was used to measure starlight deflection, confirming Einstein's theory of general relativity, with results showing light ...
[60]
The eclipse that proved Einstein right - BBC
Oct 20, 2023 · These observations confirmed Albert Einstein's theory of general relativity, which describes gravity as the curvature of spacetime. This ...
[61]
Finding Neptune: How we discovered the eighth planet
Feb 10, 2022 · In light of this analysis, it turns out Le Verrier and Adams' incomplete understanding of perturbation theory led them to make two mistakes.
[62]
Historical perspective [This Dynamic Earth, USGS]
Jul 11, 2025 · According to the continental drift theory, the supercontinent Pangaea began to break up about 225-200 million years ago, eventually fragmenting ...Missing: validation | Show results with:validation
[63]
January 6, 1912: Alfred Wegener Presents His Theory of Continental ...
Jan 1, 2019 · On January 6, 1912, he made the first presentation of his hypothesis of continental drift at a meeting of the German Geological Society in Frankfurt.Missing: validation | Show results with:validation
[64]
Expert: no evidence U.S. recovered "nonhuman" remains from UFOs
Jul 27, 2023 · CHICAGO (CBS) -- "Extraordinary claims require extraordinary evidence"; that's the advice from one space historian after a former military ...
[65]
Here's what the Pentagon's former UFO hunter learned on the job
Jan 27, 2024 · "Carl Sagan popularized the maxim that 'extraordinary claims require extraordinary evidence,'" Kirkpatrick wrote. "This advice should not be ...
[66]
The secret messages behind the lab-leak cover-up - UnHerd
Jul 28, 2023 · The “super secret” discussions show this arrogant quartet boasting about success, misleading the media, sneering at journalists and making fun ...
[67]
Covid origin: Why the Wuhan lab-leak theory is so disputed - BBC
Mar 1, 2023 · What is the lab-leak theory? It's a suspicion that the coronavirus may have escaped, accidentally or otherwise, from a laboratory in the central ...Missing: Sagan | Show results with:Sagan
[68]
The COVID Lab-Leak Theory, Jeffrey Sachs, and Peter Daszak
Mar 3, 2023 · Nowhere is the lab-leak debate more personal than among the experts investigating the origins of COVID.
[69]
Gender Dysphoria and Suicide - Where's the Extraordinary Evidence?
Mar 24, 2023 · ... Extraordinary claims require extraordinary evidence” is applied to gender ideology, and in particular the practices of “gender affirming ...
[70]
Understanding the Drive to Medically Transition as a Mental Disorder
Jul 9, 2025 · As Carl Sagan famously put it, extraordinary claims require extraordinary evidence. Yet despite years of research and growing international ...
[71]
[PDF] Cantor fact-check of AAP - Toronto
(Extraordinary claims require extraordinary evidence, and all that.) As I ... More than two devel- opmental pathways in children with gender dysphoria?
[72]
Cold fusion - → The smoke clears - Understanding Science
They and the other scientists who “reproduced” cold fusion, only to later retract their results, failed to perform adequate tests to evaluate their ideas. And, ...
[73]
Cold Fusion, Polywater & N-Rays: Notable Scientific Blunders ...
Jul 4, 2019 · “Scientific blunder has to do with bad science, but I define it further… ... Cold fusion, the last example cited by Shechtman in his ...