It is a heterodox school of political economic thought. Marxian economics comprises several different theories and includes multiple schools of thought which are sometimes opposed to each other. In many cases, its analysis is used to complement or supplement other economic approaches. Marxian economics concerns itself variously with the analysis of the crisis in capitalism, the role and distribution of the surplus product and value in various types of economic systems, the nature and origin of economic value, the impact of class and class struggle on economic and political processes, and the process of economic evolution.