The legitimate purpose of abstraction in social science is never to get away from the real world but rather to isolate certain aspects of the real wo… - Paul Sweezy

Capitalist society is characterized by a degree of labor mobility much greater than prevailed in any previous form of society.

The expansion of value, which is the objective basis or main-spring of the circulation M-C-M, becomes his subjective aim, and it is only in so far as the appropriation of ever more and more wealth in the abstract becomes the sole motive of his operations that he functions as a capitalist, that is, as capital personified and endowed with consciousness and a will. Use values must therefore never be looked upon as the real aim of the capitalist; neither must the profit on any single transaction. The restless never-ending process of profit-making alone is what he aims at.

It seems obvious that in this way the economist avoids a systematic exploration of those social relations which are so universally regarded as having a relevance to economic problems that they are deeply imbedded in the everyday speech of the business world. And it is even more obvious that the basic point of view which modern economics has adopted unfits it for the larger task of throwing light on the role of the economic element in the complex totality of relations between man and man which make up what we call society.