Some people disagreed with this reductionist viewpoint. For one, William James, an American, described consciousness as a stream that continually changes, and it cannot be reduced to elements. James still believed that consciousness could be studied, but he was interested in the functions of consciousness rather than its elements. His focus on the functions of consciousness was motivated by (a) his pragmatic philosophy, which means he was interested in the usefulness of things and ideas rather than their ultimate explanation, and (b) by Darwin's theory of evolution, which had suggested that every creature's features had evolved for some purpose. Thus, human consciousness must have some purpose or function, and James wanted to understand what that purpose was.