Résumé : AbtstractIn this work, I will explain the notion of intentionality from the point of view of perception and in particular, the immediate mental constitution of objects. To do this, I will follow the works of the Franciscan theologian and philosopher, Pierre de Jean Olivi (1248 - 1298). I will explain the general context, namely the debates surrounding the Eucharist, the difference between transubstantiation and consubstantiation, and the Latin term “species." I will then focus on the problem of intention and its medieval sources in addition to the defence of its immediacy according to de Jean Olivi. In the end, this paper demonstrates an attempt at understanding the structure of human ideas by observing the major problem of intentionality in the mediaeval age.