The use of the term "middle class" as "not poor" is relatively recent, and likely as a result of the efforts to divide the working class.

The working class is anyone who relies on wages for their survival. Middle class has meant several things, including the new and powerful class that led the French Revolution (middle between the aristocracy and peasants). In Marxism it refers to small business owners who are still beholden to large business owners, professionals (like, professions: doctor, lawyer, engineer) or middle managers. They either profit from the wage earners or earn a salary to oversee them.

Some people do not agree with the inclusion of middle management or professionals because they still depend on their wages (salary) to survive.

The idea that a unionized auto worked would be called middle class is silly, according to these older definitions.