Starting from a reflection on the theory of fictional discourse, with special attention to the Medieval West, the study considers some issues where philosophy and theology come into contact with some thorny historical situations: despite the theoretical refusal of every king of fiction, we examine the poetry and thought of Peter of Blois (twelfth century) concerning the permissibility of poetry; we look in detail at the discussing of the material truth of the fires of Hell prior to the resurrection of the body (a question that sharply divided the Platonising Franciscans from the Aristotelian Dominicans); we follow the long gestation of the notion of a juridical fiction, the fictio iuris that, deriving from Roman Law allowed the Franciscan Order to acquire juridical personality in the dispute over the permissibility for the Order to own anything whatsoever, in line with the Rule of St Francis: this long and complex process opened the way to the fundamental distinction between a person and a juridical person, both in canon and in civil law.