The Thomas Theorem of sociology was first posited by W.I. and Dorothy Swain Thomas in their 1928 book “The Child in America.” In this book, the authors present a case study of a mentally disturbed prisoner who, after overhearing mumbling among his fellow inmates and mistakenly believing that they were insulting him, violently attacked them. The theorem suggests that it does not matter what the other inmates were actually saying, because the consequences were based on the attacking inmate’s perception.
The Thomas Theorem has been used as a concept within the broader symbolic interactionism theory in sociology. This theory suggests that people within a society communicate via shared symbols and meanings, and that society is composed of these persistent individual interactions. Our comprehension of these symbols helps us to interact with one another by allowing us to understand expectations and communicate clearly. In the Thomas Theorem, the way an individual perceives the meaning of the symbols in the environment dictates that individual’s reaction regardless of alternate meanings of the symbol.
Sociologist Robert K. Merton took the principles of the Thomas Theorem and expanded them to devise the concept of the self-fulfilling prophecy in 1948. This idea holds that if expectations surrounding an individual or group suggest a certain outcome or behavior, then that individual or group may conform to those expectations in behavior. Put another way, our perception of someone can cause them to behave in a way that supports that belief, whether our idea was originally based in reality or not.
Perhaps one of the most widely-known modern examples of the Thomas Theorem is the case of Trayvon Martin. In this example, George Zimmerman perceived the young Martin to be a threat to his neighborhood before establishing contact with him. He then reacted in a defensive and violent manner to what may likely have been a non-threatening situation. The consequences were also real, with Martin killed due to the perception of threat.