Confession of ignorance or lack of words, I don't know what enjoys a long tradition, which spans from the Latin world to modern Europe, and goes through mysticism and rhetoric, psychology and philosophy, poetic production and prose. .As an expression of an experience at the limits of the speakable, I don't know what (French je ne sais quoi or Italian non so che) has given rise to brilliant reflections, dialogues and treatises. In a special way, between the 17th and 18th centuries, with the contributions of Bouhours, Leibniz, Feijoo, Marivaux or Montesquieu, I don't know what will arouse around him the most important concepts with which the modern aesthetics of which we are heirs will gradually take shape. . Feeling, taste, grace, sympathy, ease, surprise, delicacy, charm, art or nature, are notions that cover those areas of the aesthetic experience that we do not always know how to explain.