Karl Marx was a philosopher who believed that capitalism was flawed and that socialist economic approaches would yield better results. His work influenced a wide range of later economists and philosophers. The merit of his work is still heavily debated.
While Marx wrote on a great number of topics, his work on economic theory is most well known, and his economic theories continue to serve as a framework for various discussions. Social justice work, in particular, often cites Marxist ideas, and his method of framing power relationships extends, in the academic world, far beyond economics.
His critiques of capitalism are also well known. However, Marx expressed a mixed view of capitalism. While he held that it was inherently flawed, he viewed it as a natural progression for cultures. In his view, capitalism was a necessary step on the road toward a socialist, and eventually communist, society.
The fall of the Soviet Union and other communist nations did not signal an end of communism. China, for example, continues to embrace Marxist ideals, and leaders believe that their recent embrace of capitalist principles is a necessary step in achieving a truly communist nation. Nations in Northern Europe also implement a number of socialist policies influenced by Marx's work.