Thomas theorem

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The Thomas theorem is a theory of sociology which was formulated in 1928 by William Isaac Thomas and Dorothy Swaine Thomas (1899–1977) :

If men define situations as real, they are real in their consequences.[1]

In other words, the interpretation of a situation causes the action. This interpretation is not objective. Actions are affected by subjective perceptions of situations. Whether there even is an objectively correct interpretation is not important for the purposes of helping guide individuals' behavior.

The Thomas theorem is not a theorem in the mathematical sense.

In 1923, W. I. Thomas stated more precisely that any definition of a situation would influence the present. In addition, after a series of definitions in which an individual is involved, such a definition would also "gradually [influence] a whole life-policy and the personality of the individual himself".[2] Consequently, Thomas stressed societal problems such as intimacy, family, or education as fundamental to the role of the situation when detecting a social world "in which subjective impressions can be projected on to life and thereby become real to projectors".[3]

See also[edit]


  1. ^ The child in America: Behavior problems and programs. W.I. Thomas and D.S. Thomas. New York: Knopf, 1928: 571–572
  2. ^ The Unadjusted Girl. With Cases and Standpoint for Behavioral Analysis. W.I. Thomas. N.Y.: Evanston; London: Harper & Row, 1967: 42
  3. ^ Social Behavior and Personality. Contribution of Thomas to Theory and Social Research. Edmond H. Volkart [ed.] N.Y.: Social Research Council, 1951: 14

Further reading[edit]

  • Merton, R. K. (1995). "The Thomas Theorem and the Matthew Effect". Social Forces. 74 (2): 379–422. doi:10.1093/sf/74.2.379. JSTOR 2580486.
  • Smith, R. S. (1995). "Giving Credit Where Credit Is Due: Dorothy Swaine Thomas and the 'Thomas Theorem'". The American Sociologist. 26 (4): 9–28. doi:10.1007/bf02692352. JSTOR 27698742.