The positive/normative dichotomy in economics was first introduced by Nassau William Senior and John Stuart Mill in an effort to establish the scientific character of political economy. To this end, they have advocated a tri-dimensional neutrality of the scientific economic discourse: practical (vs. the art of policymaking), ethical and political. The purpose of this chapter is to present the specific terms of the original positive/normative distinction, which aimed to defend the very existence of the young discipline, introducing thus the very first principles of economic methodology. After a thorough examination of the different aspects of the triple demarcation of political economy vis-à-vis economic policy, ethics and political ideology, the classical value neutrality thesis is critically appraised. In the last section, the positive/normative distinction in the twentieth century, in 1932 with Lord Robbins and then again in 1953 with Milton Friedman is examined. It is concluded that this was made at the expense of the real meaning of the classical dichotomy.