At the beginning of the 20th century, there was a drastic change in the study of Political Science. Social sciences began to adopt the methods of natural sciences like observation, survey, and measurement. This phase in Political Science is attended by a decisive reorientation of the discipline in terms of the methods it used. The notable exponents of this “scientific politics” were Charles Merriam, Harold D. Lasswell, George Catlin and Arthur Bentley. David Easton was very critical of the scientific politics, and was the most ardent advocate of Post-Behavioralism.