Derived from the Greek pathos and the Latin passio, the French word passion in used in the Middle Age to designate a suffering and then a violent affection. After the Treatise on passions of Galen, it is only during the 17th century that physicians (like Cureau de la Chambre) and ecclesiastics (Coëffeteau, Senault) write books about the passions. In his Treatise on the passions of the soul (1649), Descartes emphasises a dualist approach body/mind, while Spinoza uses in his Ethics (1677) a monist conception. Pinel recommends to oppose the different passions between them in his “moral treatment” (1800). Esquirol writes a medical thesis on the passions (1805) and describes an affective (or reasoning) monomania (1838). Inside the French classification of chronic delusional states by their themes, Pottier isolates the delusion of “persecuted–persecutors” reasoning (1886). Serieux and Capgras develop its description in their “vindication (revendication) delusional state” (1909). Four years later (1913), the book of Maurice Dide (1873–1944), a French alienist working at Toulouse, is published in the context of the new classification of delusional disorders by “mechanisms” (interpretation, hallucination, imagination) and constitutions. The author describes three great groups of passionate idealists: 1) love, either profane, or religious, but always chaste, sudden, based on an erroneous affective judgement, a fixed inclination, mechanisms of passive contemplation and of admiration; 2) goodness, concerning philanthropists, religious and social reformers (Jean de Leyde, Saint-Simon, Cabet), idealists of the nature (François d’Assise, Rousseau, Tolstoï); 3) beauty and justice, leading to cruelty (the most important chapter). The idealism of the esthete is egocentric, relies on an overdeveloped personality (D’Annunzio) and can reverse in moral and physical cruelty (Sade). The passionate idealism of the justice can also be egocentric: it corresponds with the “vindication (revendication) delusion” (overdeveloped personality, instability, sudden beginning, intellectual excitation, capacity of conviction, dangerous behaviour). On another hand, the altruistic idealism of the justice is either individualistic (regicides, crimes of anarchists), or synthetic, with more moderate personality disorders, but implacable reforming fanaticism (Torquemada, Calvin, Robespierre). At last, Dide studies the most pathological class of “instable pseudo-altruist vindictive” lunatics, which present comorbidity with delusional and mood disorders (Marat). The conclusion of the book emphasizes on the prevalence of disorders of the affective faculties rather than of the intellectual ones and on the intensity of the passions among the idealists. They suffer from a personality disorder rather from a psychotic disorder. In 1921, Clérambault describes the passionate delusions or syndromes, subdivided into “vindication”, erotomania and jealousy ones. He distinguishes erotomania from Dide's passionate idealism of love. Guiraud (1942) tries to maintain the autonomy of the two groups. But French manuals of psychiatry, since Henri Ey (1960) valid Clerambault's classification of passionate psychosis, included into the chronic delusional disorders (paranoia).