This is the way the mind apprehends reality, but not the way reality is produced itself. Reality exists outside the thoughts of people. Move from the simple relations, such as division of labor, labor to the level of the state, exchange between nations and the world market. This is the proper methodological path. The more simple the abstraction the more developed the concrete category.
Labor is an abstract category, but it represents many different forms.
Only when in reality a category is more complex does abstraction become possible. This occurs only in the most modern society. Each of these categories used in political economy are abstractions. However, they are the product of historic relations, and posses their full validity only for and within these relations. All categories and abstractions must be considered within their historical location.