« Root » and « Branches » : Logic and Kabbalah in The Work of Moses Hayyim Luzzatto Logic is generally considered to be opposed to the mystical and esoteric lore of Kabbalah. In contrast to this view, this paper deals with the close relationship that links together these two domains in the work of Moses Hayyim Luzzatto (1707-1746). The first section describes the basic features of Luzzatto's logic. The second section focuses on two specific and fundamental rules of that logic : « distinction » and « gradual progression ». The third section shows that these rules of Luzzatto's logic are also principles of his Kabbalah. It also stresses how the domain of logic is a propaedeutic to the « science of the divine » i. e., Kabbalah. The final section shows that the Lurianic writings are a significant source of Luzzatto's kabhalistic methodology.