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Thomas Theorem

Thomas Theorem

Author: Sophia Tutorial

This lesson will explain the Thomas Theorem and define ethnomethodology.

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What's Covered

This tutorial will cover the following topics of sociology:

  1. Thomas Theorem
  2. Ethnomethodology


The Thomas Theorem states that situations defined as real, are real in their consequences. This seems intuitively easy to understand, but in actuality is a bit more complex.


Picture a small child who believes in ghosts or the boogeyman underneath his bed. He is terrified of them. It doesn't matter that they're not there and they're not real, but he thinks they are, so therefore that situation is real in its consequences.

The fear that he's feeling, the boogeyman underneath his bed that's causing him to get up in the middle of the night and run into his parent's room, is a real thing. It doesn't matter that it's not real in reality; situations defined as real, are real in their consequences.

The Thomas Theorem also applies to more complex, consequential, and broader societal issues, like race. People of different races are no different biologically, but society has constructed notions of racial difference over the years. Even though ideas about racial difference are social constructions, they have real consequences for people of color in that their opportunities and life chances have been constrained for generations, which has been exceedingly hard to overcome.

Think About It

Suppose a politician says that all poor people are poor because they are lazy and don't want to work hard. It this statement true? In most cases, no, but because he thinks that, it will affect the policy he wants to make, which in turn can have real world consequences. If his belief in the stereotype of ‘welfare queens’ prompts his decision to cut all aid to poor people because he feels they're simply squandering it, it will have a definite real world consequence for the poor people affected by his policy.

Term to Know

Thomas Theorem

A theory named after W.I. Thomas and Dorothy Thomas that states: "situations defined as real, are real in their consequences."


In the 1960’s, Harold Garfinkel argued that it is necessary to study the way in which people themselves make sense of their everyday surroundings. This is achieved by recording, dissecting, and analyzing the underlying assumptions of everyday action in specific cultures and subcultures, a process known as ethnomethodology. The researcher’s job is to go out, record, and understand how people use assumptions to make sense of their everyday world. Often this is done by thickly describing what is seen--called ‘thick description’ by social scientists.


Thick description works like this: Suppose you are observing John eating at the dinner table. Now, the observations are not simply, “John sat at the dinner table, picked up a spoon, and ate.”

You would observe that John walked a particular way to sit down at the dinner table. John's clothes looked a certain way. The table was set with the spoon on the right, and the fork on the left. The plate was in front of him and he had two small plates to the side. You would describe how the plates look. You’d describe the tablecloth, if there was one, and the walls and floors. You’d describe how people interacted, in every mundane interaction, which may seem incredibly long, but doing this helps you to see the underlying assumptions that in turn help people make sense of their everyday surroundings.

Another way to become cognizant of the constructed nature of social reality is to disrupt patterns of interaction that people assume will be there.


Working in retail, people tend to follow the culture’s assumptions about how their interactions are supposed to progress:
“Hi, how are you doing today?”
“Good, and you?”
“Good, thanks. Did you find what you needed?
“Yes. Have a great day. Thanks.”

However, what if you broke the rules? What if somebody came up to you and asked how you were doing, and you said, “Well, actually, I'm awful. I'm having digestive issues, my brother just went to jail, and my mom is a drunk.” What would that person think? It would make them aware that they take for granted these cultural constructions of a professional transaction. There's nothing necessarily natural about how that type of social transaction is supposed to unfold, but people culturally construct what is supposed to happen, and that is taken for granted.

Big Idea

Ethnomethodology is beneficial, Garfinkel maintained, because it helps people to become cognizant of how social reality is created and constructed, and the assumptions that underpin that reality.

Term to Know


Harold Garfinkel's term for the study of the way people come to understand the world and their surroundings.


Today you learned about the Thomas Theorem and a brief introduction to ethnomethodology.

Good luck!

Source: This work is adapted from Sophia author Zach Lamb.

Terms to Know

Harold Garfinkel's term for the study of the way people come to understand the world and their surroundings.

Thomas Theorem

A theory named after W.I. Thomas and Dorothy Thomas that states: "situations defined as real, are real in their consequences."