Heinrich Rickert (1863-1936) was one of the leading neo-Kantian philosophers in Germany and a crucial figure in the discussions of the foundations of the social sciences in the first quarter of the twentieth century. His views were extremely influential, most significantly on Max Weber. The Limits of Concept Formation in Natural Science is Rickert's most important work, and it is here translated into English for the first time. It presents his systematic theory of knowledge and philosophy of science, and deals particularly with historical knowledge and the problem of demarcating the natural from the human sciences. The theory Rickert develops is carefully argued and of great intrinsic interest. It departs from both positivism and neo-Hegelian idealism and is worked out by contrast to the views of others, particularly Dilthey and the early phenomenologists.