The Metamorphoses of Capital and Their Circuit

Capitalist theory of value is based on the idea that real, living labor can be exploited to extract more money from a company than they are giving back. The ideas were long existed before robertus discovered surp value. Capitalists exploit workers in order to make profit for themselves and their companies. This explains how capital actually exists as capital - it's just being used by capitalists to create new products which will then go into production.