If the notion of mysticism seems to go without saying for the Middle Ages, it seems to be the result of a misunderstanding. For if the historiography of the nineteenth ecentury willingly denigrated with this word what, in medieval literature, seemed to it cutesy, irrational or extravagant, medieval authors use the adjective "mystical" to designate something else: a certain way of interpreting Scriptures (mystical meaning), a way of speaking about God (mystical theology), belonging to the same Church (mystical body). It is therefore advisable to return to the texts, by asking them these questions. When is the word "mystical" used in medieval works, and what does it mean? Conversely, in the works known today as "mystical", how is that which falls within this category named, defined, understood by the authors themselves? Is it relevant to include in the same genre texts as diverse as visions, devotional literature,the analyzes of contemplation, the soul's routes to God, the Mystical theology of pseudo-Dionysius? From the end of the Patristic period to the beginning of the Renaissance, has the meaning of the word "mystical" remained stable, or has it evolved? Basically, can we say that the modern notion of mysticism has its origin in medieval times?