One answer would be that he was one of the severest and original critics of the capitalist system. He was also a critic of class structure in societies. But, because this course is really devoted to what we call classical social theory, we study him because we regard him as a very important, outstanding thinker of the 19th century. When we get to max weber, we"ll see that weber calls marx a great thinker. As we can see from the chapters, one of the most important contributions that marx makes was in the area of historical sociology. As discussed in the tocqueville lecture, the historian studies the unique and unrepeatable processes of history, i. e. there was only one julius caesar, one napoleon, etc. A good historian is also a good sociologist. But, the historical sociologist really focuses attention on what we would call causes and consequences. They really want to explain things; they"re not just telling a story.