Origin and the definition of the situation
Thomas and Thomas (1928) wrote the sentence in a book on children's behavior problems, citing a prisoner who attacked people talking to themselves on the street because he believed they were cursing him. To understand behavior, one must know how actors define a situation, not only its objective features. The idea grew out of the concept of the definition of the situation developed in Thomas and Znaniecki's The Polish Peasant in Europe and America (1918–1920) and Thomas (1923). Individual definitions always compete with social definitions supplied by family and community, and this tension was used to explain the disorganization and reorganization of immigrant communities.
Merton and the self-fulfilling prophecy
Merton (1948) built on the Thomas theorem to formulate the self-fulfilling prophecy: a false definition of a situation evokes new behavior that makes the originally false conception come true. His example was a rumor that a bank is insolvent, which triggers a run that actually ruins the bank. Merton (1995) described the theorem as close to the single most consequential sentence in social science, traced its intellectual lineage and highlighted Dorothy Thomas's contribution as co-author. Smith (1995), by contrast, questioned the way the theorem came to be treated as a classic.
Theoretical influence and empirical research
The Thomas theorem provided an important foundation for Blumer's (1969) symbolic interactionism, Berger and Luckmann's (1966) social construction of reality and Goffman's (1974) frame analysis. In education, Rosenthal and Jacobson (1968) reported a Pygmalion effect in which teacher expectations could affect student achievement, and Jussim (1986) systematically reviewed the size and conditions of self-fulfilling prophecies, concluding that effects are generally small but real. Biggs (2009) formalized the mechanisms and limits of self-fulfilling prophecies from the standpoint of analytical sociology. Volkart (1951) collected and introduced Thomas's theoretical work.
FAQ
- What is the Thomas theorem in simple terms?
- If people believe a situation is real and act on that belief, the consequences of their actions are real even if the belief was not true.
- How is it related to the self-fulfilling prophecy?
- Merton developed the self-fulfilling prophecy from the Thomas theorem. The theorem is the general principle that definitions of situations produce behavior; the self-fulfilling prophecy is the special case in which a false definition makes itself come true.
Sources reviewed: 2026-10-26
References
- Thomas, W. I., & Thomas, D. S. (1928). The Child in America: Behavior Problems and Programs. New York: Knopf.
- Thomas, W. I., & Znaniecki, F. (1918–1920). The Polish Peasant in Europe and America (5 vols.). Boston: Badger.
- Thomas, W. I. (1923). The Unadjusted Girl. Boston: Little, Brown.
- Merton, R. K. (1948). The self-fulfilling prophecy. Antioch Review, 8(2), 193–210.
- Merton, R. K. (1995). The Thomas theorem and the Matthew effect. Social Forces, 74(2), 379–424.
- Smith, D. S. (1995). The Thomas theorem: A sociological classic? Social Forces, 74(2), 451–458.
- Blumer, H. (1969). Symbolic Interactionism: Perspective and Method. Englewood Cliffs, NJ: Prentice-Hall.
- Berger, P. L., & Luckmann, T. (1966). The Social Construction of Reality. Garden City, NY: Doubleday.
- Goffman, E. (1974). Frame Analysis: An Essay on the Organization of Experience. New York: Harper & Row.
- Rosenthal, R., & Jacobson, L. (1968). Pygmalion in the Classroom. New York: Holt, Rinehart & Winston.
- Biggs, M. (2009). Self-fulfilling prophecies. In P. Hedström & P. Bearman (Eds.), The Oxford Handbook of Analytical Sociology (pp. 294–314). Oxford: Oxford University Press.
- Jussim, L. (1986). Self-fulfilling prophecies: A theoretical and integrative review. Psychological Review, 93(4), 429–445.
- Volkart, E. H. (Ed.). (1951). Social Behavior and Personality: Contributions of W. I. Thomas to Theory and Social Research. New York: Social Science Research Council.