The Thomas theorem of sociology states "If men define situations as real, they are real in their consequences," according to the Blackwell Encyclopedia of Sociology Online. The objective reality of a situation doesn't matter as much as someone's perception of what someone believes is happening. Sociologist W.I. Thomas published his theorem in 1928.
Prof. Ernie Guyton of Georgia Perimeter College reveals that one example of this theorem is the American invasion of Iraq. Factions of the U.S. government believed Iraq's leaders had weapons of mass destruction and were capable of using them against Americans in the United States. Therefore, the U.S. military invaded Iraq in 2003 as a preemptive measure to try to prevent such a massive attack.
Another example of the Thomas theorem is the case of Trayvon Martin's death. Defendant George Zimmerman perceived Martin as a threat and then killed him, according to Nathan Palmer of Sociology in Focus. Zimmerman is heard in recordings claiming that Martin is "up to no good or on drugs." The neighborhood watch officer shot and killed Martin and then claimed self defense, even though Martin was unarmed.
Thomas was elected president of the American Sociological Society in 1927. The sociologist lived from 1863 to 1947, mostly in Chicago.