The distinction between the ‘classical’ monetary theory and ‘quantity’ theory has been proposed in literature on money and banking. The overall feature of the classical theory of money is that it holds one principle of regulation for each kind of issue (metallic money, bank issues and paper money) whereas the quantity theory applied the causality and proportionality postulates for all kinds of monies. Without claiming to adjudicate the validity of such a distinction, the paper investigates the foundation of each tradition. In this respect, this paper, respectively, examines, and provides a survey of the secondary literature on, Cantillon's Essai and the Hume's Discourses.