 Interest in exploitation as a feature of economic exchange is thus almost as old as philosophy itself. It was not until the 19th century, however, that exploitation as a feature of employment relationships came to be a subject of philosophical and political concern. In a sense, of course, the employment relationship is simply another instance of economic exchange, with the laborer selling his or her work in exchange for money in the form of wages. But two ideas led many people to think that there was something special about labor. The first was a belief that labor is the ultimate source of all economic value. The second was the belief that labor morally entitles the laborer to the full value of that which he or she has produced.