Certainty in Religious Belief Scale

Abstract

The Certainty in Religious Belief Scale (CRBS), originally conceptualized and formulated as “The ‘Beliefs’ Test” by British psychologist Robert Henry Thouless in 1935, is a classic psychometric instrument designed to isolate and quantify the psychological tendency toward epistemic certitude in the domain of religious and metaphysical assertions. Distinct from conventional instruments measuring theological orthodoxy, religiosity, or church affiliation, the CRBS measures the structural conviction or subjective probability with which beliefs are held, completely independent of their theological direction or doctrinal content. The scale originally featured 40 propositions encompassing theological doctrines, empirical claims, and philosophical postulates, though standard psychometric practice retains the 25 distinctively religious and metaphysical items. Participants rate each proposition on a symmetrical 7-point bipolar continuum ranging from complete conviction that the statement is true (+3) to complete conviction that the statement is false (−3), centered upon absolute uncertainty (0). Scoring is executed via a modulus transformation in which the absolute values of ratings are averaged across items, producing an aggregate index of subjective certainty ranging from 0.00 to 3.00. Thouless’s foundational normative study of 138 adults at the University of Glasgow yielded a sample mean certainty of 2.13 (SD = 0.32), revealing that religious propositions tend to evoke high epistemic certitude characterized by bimodal response distributions, regardless of whether participants affirm or reject the doctrines. Subsequent psychometric reappraisals, notably by L. B. Brown (1962), demonstrated that epistemic certainty constitutes a cognitive style that operates orthogonally to general cognitive ability and doctrinal orthodoxy, making the CRBS a foundational tool for research into religious dogmatism, cognitive closure, and ideological polarization.

Keywords

Certainty in Religious Belief Scale, Robert H. Thouless, epistemic certainty, religious conviction, psychology of religion, dogmatism, cognitive style, religious doubt, orthodoxy, attitude polarization, need for closure, psychometrics

Authors

The Certainty in Religious Belief Scale was developed by Robert Henry Thouless (1894–1984), an eminent British psychologist who served as Lecturer in Psychology at the University of Glasgow (1926–1938) and subsequently as Reader in Educational Psychology at the University of Cambridge. Thouless was a pioneering scholar in the psychology of religion, social psychology, philosophical logic, and psychical research, authoring seminal texts including An Introduction to the Psychology of Religion (1923) and Straight and Crooked Thinking (1930). Thouless served as President of the British Psychological Society from 1949 to 1950. Subsequent psychometric investigations and factorial re-examinations of the instrument were conducted by L. B. Brown at the Victoria University of Wellington and Massey University, New Zealand.

Purpose

The primary purpose of the Certainty in Religious Belief Scale is to distinguish the cognitive content of a belief from the epistemic certitude with which that belief is embraced or repudiated. While early 20th-century psychometricians focused primarily on measuring the degree of orthodoxy, traditionalism, or nominal religious observance, Thouless recognized that two individuals holding diametrically opposed positions (e.g., a fundamentalist Christian affirming the historical veracity of scripture and a militant atheist denying the existence of God) might share an identical underlying psychological orientation: absolute epistemic certainty.

In empirical psychology and cognitive science, the instrument serves several distinct functions:

• Decoupling Directionality from Extremity: The CRBS assesses the intensity of conviction independent of doctrinal polarity, allowing researchers to evaluate dogmatic cognitive styles across traditional theists, nontheists, deists, and philosophical naturalists.
• Investigation of Cognitive and Personality Correlates: The instrument facilitates empirical investigation into how epistemic certitude correlates with constructs such as cognitive flexibility, general intelligence, authoritarianism, and tolerance of ambiguity.
• Clinical and Pastoral Applications: In clinical and counseling psychology, variations of the CRBS provide insight into epistemic rigidity, religious scrupulosity, existential anxiety, and the psychological crisis precipitated by the collapse of previously unshakeable belief systems.
• Sociological and Cross-Cultural Research: The scale offers a standardized framework for tracking shifts in secularization, investigating whether modernization attenuates belief content, certitude, or both.

Psychological Construct

The psychological construct evaluated by the CRBS is epistemic certitude in metaphysical domains, defined as the subjective absence of doubt or ambivalence regarding propositions that are not susceptible to direct, unmediated empirical verification. In psychometric literature, belief systems involve both direction (the valence or ideological alignment of the proposition) and intensity (the strength of conviction, psychological commitment, and perceived invulnerability to counter-evidence).

Dimensions of the Construct

Thouless conceptualized epistemic certainty as a continuous dimension reflecting a respondent’s metacognitive evaluation of truth-value:

• Maximal Certitude (|X| = 3): Uncompromising psychological conviction. At this level, the individual perceives the proposition as self-evident or dogmatically settled, experiencing zero cognitive dissonance or openness to revision. Crucially, maximal certitude can manifest either as orthodox dogmatism (+3) or counter-dogmatic certainty (−3).
• Moderate Conviction (|X| = 2): Strong probabilistic inclination toward truth or falsehood, accompanied by implicit recognition that the proposition remains inferential rather than axiomatic.
• Tentative Alignment (|X| = 1): Explicit cognitive ambivalence, characterized by low confidence and an awareness that existing evidence is inconclusive.
• Epistemic Neutrality or Absolute Uncertainty (|X| = 0): Complete suspension of judgment, corresponding to a state of philosophical agnosticism or profound epistemic indecision.

Thouless demonstrated that when individuals respond to religious propositions, their ratings do not follow the standard Gaussian distribution typical of empirical beliefs (e.g., historical or physical claims). Instead, responses to religious propositions exhibit a pronounced U-shaped or bimodal distribution: participants cluster predominantly at the extreme endpoints (+3 and −3), with markedly few responses occupying the moderate or uncertain categories. This empirical phenomenon reveals that metaphysical propositions tend to activate an “all-or-none” cognitive mechanism, wherein individuals adopt polarized epistemic commitments.

Theoretical Framework

The Certainty in Religious Belief Scale is anchored in Thouless’s theoretical model of doxastic commitment and cognitive defense, formulated during an era marked by the integration of functionalist psychology, logical positivism, and early cognitive science. Thouless posited that human cognitive functioning operates across two distinct domains of proposition processing: empirical-probabilistic assertions and metaphysical-affective assertions.

Empirical vs. Metaphysical Propositions

Under Thouless’s model, when healthy cognitive agents evaluate scientific or empirical statements (such as demographic statistics or physical constants), their degree of certainty correlates proportionally with the quantity and quality of empirical evidence available. Belief in empirical claims is theoretically probabilistic, fluid, and susceptible to revision upon the presentation of novel data. Conversely, when agents evaluate metaphysical, theological, or ultimate existential propositions, the rational calculus of evidence is frequently superseded by psychological forces.

The Principle of Certainty Tendency

Thouless hypothesized the existence of an endogenous cognitive drive termed the “tendency to certainty.” According to this principle, the human mind experiences sustained epistemic ambivalence regarding existential questions (e.g., death, morality, cosmic origin, divine agency) as psychologically threatening and cognitively taxing. To reduce the tension of ambiguity, individuals employ defensive cognitive strategies that polarize intermediate probabilities into subjective certainties. This theoretical proposition anticipates subsequent developments in social cognitive psychology, such as Leon Festinger’s theory of cognitive dissonance and Arie Kruglanski’s need for cognitive closure.

Orthodoxy and Counter-Orthodoxy Equivalence

A core postulate of Thouless’s theoretical framework is that the psychological architecture of certainty is structurally equivalent across opposing belief contents. An unshakeable belief that “There is a personal God” (+3) and an unshakeable belief that “There is no God” (−3) fulfill an identical psychological function: providing cognitive closure, stabilizing existential anxiety, and anchoring the respondent’s interpretive worldview. The CRBS was explicitly designed to operationalize this theoretical symmetry.

Validity

Psychometric evaluation of the CRBS has focused on construct, convergent, and discriminant validity across multiple decades of empirical research.

Construct and Discriminant Validity

In his original 1935 investigation involving 138 university students, Thouless tested several foundational validity hypotheses:

• Independence from Cognitive Ability: Thouless correlated certainty scores with standardized intelligence metrics available for a subset of his sample. Contrary to the rationalist expectation that higher general intelligence would correlate with intellectual humility and lower religious certitude, Thouless observed no reduction in certainty among participants with higher intelligence; in fact, a slight positive trend was noted. This established that the tendency toward certainty is a distinct cognitive style rather than a byproduct of cognitive deficit.
• Symmetry Across Theological Orientations: Thouless classified participants along an orthodoxy index derived from directional responses. His analysis revealed that certitude among unorthodox/skeptical participants was psychometrically indistinguishable from that of traditional orthodox believers, validating the construct as an invariant measure of cognitive extremity rather than theological conformity.
• Gender Invariance: Comparisons revealed no statistically significant differences in certainty tendencies between male and female participants, supporting cross-demographic structural stability.

Replication and Convergent Validity Studies

In a comprehensive replication and methodological extension, L. B. Brown (1962) examined the structure of religious beliefs using Thouless’s items alongside additional psychological inventories across multiple samples of university students. Brown confirmed that religious certainty constitutes a robust, identifiable psychometric dimension that correlates significantly with measures of generalized dogmatism, intolerance of ambiguity, and behavioral adherence to religious rituals, while maintaining clear discriminant divergence from verbal intelligence and socioeconomic status.

Reliability

At the time of the scale’s initial publication in 1935, modern classical test theory metrics, such as Cronbach’s alpha (introduced in 1951), had not yet been established. Thouless relied on descriptive stability, inter-item distributional consistency, and comparative subgroup analyses to evaluate instrument behavior.

Subsequent psychometric evaluations of the 25-item religious inventory have established solid reliability parameters:

• Internal Consistency: Post-hoc psychometric analyses applying modern internal consistency formulas have demonstrated robust reliability. When scored for directional religious orthodoxy (retaining positive and negative signs), the scale demonstrates exceptional internal consistency, with standardized Cronbach’s alpha coefficients typically exceeding α = .88 to .92. When scored for absolute certainty magnitude (|X|), internal consistency coefficients range from α = .78 to .84, reflecting consistent individual differences in polarization across diverse theological topics.
• Split-Half Reliability: Early split-half analyses of the certainty scores utilizing the Spearman-Brown prophecy formula indicated split-half coefficients ranging between r = .76 and .82 across balanced halves of the instrument.
• Test-Retest Stability: Studies examining longitudinal stability (e.g., Brown, 1962) have shown that while individual item directionality may occasionally shift in response to critical life events or philosophical inquiry, an individual’s mean certainty coefficient exhibits substantial temporal stability over intervals of 6 to 12 months (r > .75), demonstrating that the tendency toward certainty operates as an enduring cognitive trait.

Factor Analysis

Because the CRBS can be analyzed in two distinct forms—either as directional belief items (−3 to +3) or as absolute certainty transformations (|X| from 0 to 3)—factor-analytic investigations have revealed nuanced structural dimensions.

Factor Structure of Directional Items

When the 25 items are submitted to exploratory factor analysis (EFA) using principal axis factoring or principal component analysis with varimax or oblimin rotation (as conducted by Brown, 1962), a multidimensional structure consistently emerges, typically resolving into three to four robust factors:

• Factor 1: Classical Christian Theism / Traditional Orthodoxy: High positive loadings on foundational Judeo-Christian doctrines, including “There is a personal God,” “The world was created by God,” “Jesus Christ was God the Son,” “There is a God who is all-powerful,” and “The Bible is literally true in all its parts.”
• Factor 2: Scientific Naturalism / Materialism (Inverse Orthodoxy): High positive loadings on statements reflecting materialist metaphysics, such as “Matter is the sole reality,” “Religion is the opium of the people,” “There is no God (personal or impersonal),” and “Man has been evolved from lower forms of life.”
• Factor 3: Parapsychological and Esoteric Spiritual Realities: Salient loadings on items transcending classical denominational doctrine, including “There are spiritual realities of some kind,” “The spirits of human beings continue to exist after the death of their bodies,” and “The spirits of persons who have died can sometimes communicate with the living.”
• Factor 4: Moral Optimism and Religious Superiority: Moderate loadings on evaluative propositions such as “Right will triumph,” “Evil is a reality,” and “Christianity is a better religion than Buddhism.”

Factor Structure of Absolute Certainty Scores

When items undergo modulus transformation (|X|) prior to extraction to evaluate the structural tendency to certainty, confirmatory factor analytic (CFA) models reveal a predominant general factor (Certitude Propensity), supporting Thouless’s hypothesis of a generalized epistemic disposition toward polarization. Fit indices for a single-factor certitude model across heterogeneous student and adult populations demonstrate adequate parameters (CFI > .90; RMSEA ≤ .06), indicating that the absolute scoring metric effectively captures a cohesive latent construct.

Instrument / Measurement Tool

• Instrument Name: Certainty in Religious Belief Scale (CRBS) / The ‘Beliefs’ Test
• Author: Robert Henry Thouless, Ph.D.
• Publication Year: 1935
• Construct Measured: Epistemic certitude and extremity of conviction in religious and metaphysical propositions
• Administration Format: Self-administered, paper-and-pencil or computerized questionnaire; individual or group testing
• Target Population: Adults and adolescents aged 16 and older possessing standard reading comprehension
• Administration Time: Approximately 10 to 15 minutes
• Item Composition: 25 core religious and metaphysical propositions (retained from Thouless’s original 40-item inventory, which contained 15 nonreligious cultural and political statements now omitted due to historical obsolescence)
• Response Continuum: Symmetrical 7-point bipolar Likert-type rating format:
  • +3: I am completely certain that this statement is true.
  • +2: I am almost certain that this statement is true.
  • +1: I think that this statement is true, but I am not at all certain.
  •  0: I am completely uncertain about this statement.
  • −1: I think this statement is false, but I am not at all certain.
  • −2: I am almost certain that this statement is false.
  • −3: I am completely certain that this statement is false.
• Scoring Procedures:
  • Certainty Index (Primary Metric): Convert each item score to its absolute value (|X|), eliminating directional signs (− and +). Absolute item values range from 0 to 3. Sum these transformed scores across all 25 items and divide by 25:
    
    Certainty Index = (∑ |Item Score|) / 25
    
    The resulting mean certainty index ranges from 0.00 (absolute pervasive uncertainty) to 3.00 (absolute complete certainty across all propositions).
  • Orthodoxy / Belief Direction Index (Secondary Metric): Retain positive and negative algebraic signs to evaluate directional theistic commitment, reverse-scoring secular/materialist items as appropriate.

Permissions & Fee and Test Year

The Certainty in Religious Belief Scale was formulated by Robert H. Thouless and published in 1935 in the British Journal of Psychology, an official journal of the British Psychological Society (BPS). Given that the original publication occurred in 1935, the primary scale items are widely considered to reside in the public domain under historical academic copyright terms across most international jurisdictions. The instrument is accessible without licensing fees for noncommercial scientific research, psychometric education, and clinical investigation. Investigators utilizing the instrument are expected to maintain academic attribution by citing Thouless’s foundational 1935 paper and subsequent validation literature.

References

• Brown, L. B. (1962). A study of religious belief. British Journal of Psychology, 53(3), 259–272. https://doi.org/10.1111/j.2044-8295.1962.tb00833.x
• Thouless, R. H. (1923). An Introduction to the Psychology of Religion. Cambridge University Press.
• Thouless, R. H. (1930). Straight and Crooked Thinking. English Universities Press.
• Thouless, R. H. (1935). The tendency to certainty in religious belief. British Journal of Psychology, 26(1), 16–31. https://doi.org/10.1111/j.2044-8295.1935.tb00770.x
• Thouless, R. H. (1951). General and Social Psychology (3rd ed.). University Tutorial Press.
• Allport, G. W., & Ross, J. M. (1967). Personal religious orientation and prejudice. Journal of Personality and Social Psychology, 5(4), 432–443. https://doi.org/10.1037/h0021212
• Altemeyer, B. (1988). Enemies of Freedom: Understanding Right-Wing Authoritarianism. Jossey-Bass.
• Batson, C. D., Schoenrade, P., & Ventis, W. L. (1993). Religion and the Individual: A Social-Psychological Perspective. Oxford University Press.
• Kruglanski, A. W., & Webster, D. M. (1996). Motivated closing of the mind: “Seizing” and “freezing.” Psychological Review, 103(2), 263–283. https://doi.org/10.1037/0033-295X.103.2.263
• Rokeach, M. (1960). The Open and Closed Mind: Investigations into the Nature of Belief Systems and Personality Systems. Basic Books.

13. Items of the Scale (Questionnaire)