The two notions of scientific positivism and legal positivism are to be distinguished from each other. Scientific positivism refers to a specific stance in the philosophy of science, as held by the logical positivist (Vienna Circle, Wiener Kreis) in the 1920s and 1930s, and partly by its ideological successors, the logical empiricists. Logical positivists sought to define scientific methodology with the possibility of empirical verifiability, ruling out any metaphysical speculation from the realm of science. Analytical philosophy is defined as an approach, style, or mentality of "doing philosophy", with emphasis on the linguistic analysis of concepts and the avoidance of metaphysical speculation. Legal positivism, on the other hand, is equal to the idea that modern law is positive, enacted law to the effect that it can (only) be initially created, subsequently altered in content, and ultimately derogated by an act of will of the sovereign legislator (sensu largo). Moreover, positive law is distinguished from positive political morality in society by reference to its formal source of origin in legislation. In the study of law, positivism in its scientific and legal contexts has not always been kept strictly apart, as for instance Alf Ross' stance on jurisprudence bears witness of. The saga of legal positivism has evolved in the form of analytical and institutional legal positivism, while the former can be split into the two subcategories of exclusive and inclusive legal positivism on the basis of whether the rule of recognition may also entail content-bound criteria with reference to the political morality in society. Kaarlo Tuori's idea of critical legal positivism is ruled out of the domain of legal positivism strictly defined, due to the impact of Dworkinian principles of law and the elements of a Marxist conception of law in it. In general, legal interpretation has proven to be the Achilleus' heel of legal positivism, as its focus has been on the other issues, and on the concept of law and its relation to political morality in specific. The key issues of legal argumentation are then tackled with the exegetical school of law (École de l"Exégèse) that had its heyday in France and Belgium in the nineteenth century.