Political economy is essentially a historical science. It deals with historical, i.e., constantly changing materials; it first studies the special laws of production and exchange at each individual stage of development

Political economy is essentially a historical science.

It deals with historical, i.e., constantly changing materials; it first studies the special laws of each individual stage of development of production and exchange, and only after the completion of such studies can it establish the few laws which apply in general and in general and in total universality to production and exchange.

At the same time, it goes without saying that the laws applicable to a certain mode of production and the form of exchange are also applicable to all historical periods in which such modes of production and exchange have been possessed. For example, with the adoption of metal money, a series of laws applicable to all countries and historical periods that applied to the exchange of metal money came into play.

- "Anti-Dühring", The Collected Works of Marx and Engels (Volume III), P525-526# Marxist-Leninist Works #