The aim of this article is to study how Smith’s concept of system is different from what was called in the 18th century the system of Optimism developed by Malebranche and mainly by Leibniz. Jon Elster has shown the influence of the philosopher of Hanover in the architectonics of capitalism or rather – of laisser-faire. If this fact alone could encourage us to compare the two systems, another element also provides an incentive. At the very moment when Smith began his work there was a controversy opposing the supporters of the system of optimism with « Newtonians » and their three key figures in France: d’ Alembert, Condillac and Voltaire. This controversy is mainly about the concept of connections or of laws which bind the elements of a system. It followed the one which had opposed Newton with Leibniz at the very beginning of the 18th century. After presenting the system of Optimism we will compare with that of Smith on three key points: the concept of monade, the concept of system itself, with its architectonic, theoretical and political stakes, and finally the problem of maximization. Then we will propose a non leibnizian interpretation of the “invisible hand” more empathetic with Smith’s architectonics as it has appeared in our study.