The paper aims at examining the development of Lodovico Antonio Muratori's theory of imagination from the publication of "Perfetta poesia" (1706) to that of "Forze della fantasia" (1745). Muratori takes into account both the Aristotelian and the Cartesian perspective, but he elaborates his personal ideas in order to explain the functioning of imagination in the system of the faculties of the soul. In the intense correspondence with Tommaso Campailla he provides an answer to the various questions concerning the irrational nature of dreams, and the visions of enthusiasts or maniacs. In this context, he deals with the problem of the relation between spiritual reason and material phantasy, even though he doesn't seem to give a clear solution to it. Nevertheless, in Muratori's discourse on the use (and abuse) of imagination, it is possible to perceive his attempt to enrich the Catholic philosophical tradition with the new scientific vision of the world by means of an original combination of old and modern categories of thinking.