The article concerns the trends of the development of the economic thought of the 20th century. It presents the most significant projects of the economic theory which came into being in this century. The author focuses on the issue of free market, economic freedom and personal property. He shows how the views on the aforementioned issues were changing and at the same time he presents almost all main concepts of solving these problems. The author focuses primarily on some characteristic evolution of basic trends in economic theory: he examines some aspects of the theory which strayed away from fundamental categories of market, economic freedom and personal property - and then returned to them again.