This thesis examines the work On love, written in 1822 by the French writer Henri Beyle (better known by one of his many pseudonyms, Stendhal), taking it as an elaboration of an epistemology of love. It considers the book, which is about love and many other forms of passion, to be a theorization on the faculties necessary for the development of knowledge in general. This interpretation is based on the assumption that Stendhal s naming the text a treatise and considering it to be science should not be ignored, even if the text s anti-systematic form, when compared to the epistemological currents taken as a model for the writer (namely, those of sensualist inspiration), would indicate some other finality. This work proposes, then, reading On love as conceiving a theory of knowledge, one that should be understood precisely in its formal disorder, and not in spite of it. The intention is to take into consideration the treatise form under which the book is presented as a constitutive part of its epistemology, demonstrating that the latter is the effect of the radicality of its sensualist premise. Taken to an extreme, Stendhal s inscription in this school makes him question the sufficiency of the philosophicalscientific models that are available for producing knowledge about the experience of loving passion and to elaborate, even if precariously, a new form that will give expression to his understanding of the phenomenom.