What is the Thomas theorem? Restate it in your own words and provide an example of its application.

The Thomas theorem states that "if people define situations as real, they are real in their consequences." In other words, the way people define a situation becomes its reality for them.
The textbook gives the following example: suppose you're walking down the street and you witness a woman slapping a man in public. What are the possible meanings of that situation? It could be a fight or spousal abuse, or it could be a joke or a friendly greeting, depending on how hard the slap is. It could be the man has just passed out and the woman hopes to revive him. The participants could be actors shooting a scene from a film. Each of these interpretations leads to a different set of potential consequences depending on which meaning you act upon. You might intervene, call the police, laugh, ignore it, summon paramedics, or ask for an autograph. Each definition of the situation lends itself to a different approach, and the consequences are real.