Isidore Isou was born Isidore Goldstein on 29 January 1925 in Botoşani, Romania. He arrived in Paris on 23 August 1945 with a suitcase full of texts and manuscripts, a head full of ideas, and the forceful intention to bring new life to the arts and to all fields of human knowledge.

He began theorizing Letterism (Lettrisme in French; also known in English as Lettrism), the movement he founded, at the age of seventeen; its objective was to be the “the avant-garde of the avant-garde,” the successor to Surrealism, which it sought to surpass. In 1942, he experienced a flash of intuition while reading a mistake - but one that turned out to be both fertile and foundational - in the translation of a phrase by the philosopher Hermann von Keyserling: he read, “the poet dilates the vowels” [voyelles] instead of “the poet dilates the terms” [vocables]. This inspired Isou to undertake to crush words down to their letters, new creative bedrock, annihilating meaning in favor of sound. In Isou’s creative system, letters were unique creative particles aimed at a cosmic language. Letterism, however, could not be reduced to this poetry and to this letter-music alone: Isou went down many paths and explored vast fields of knowledge, pushing far past the notion of “lettrism” to map out territories using language and names entirely his own to embrace the world as he understood it.

Soon after arriving in Paris in 1945, Isou met Gabriel Pomerand, with whom he launched the Lettrist movement. Together, they organized Letterism’s first events, in 1946, along with François Dufrêne, and founded a journal (the first in a long line of journals, which often had only one issue): La Dictature Lettriste (“The Letterist Dictatorship”) that included a manifesto titled “Poetic and Musical Principles of the Letterist Movement” in which Isou sketched out the premises of his theory of poetics and music, laying the foundations for his book, Introduction à une nouvelle poésie et à une nouvelle musique (Introduction to a New Poetry and a New Music), which was published by Gallimard the following year, and which contains his first musical compositions, including his Symphony n°1: La Guerre. On 21 January of that year, Isou interrupted a performance of Tristan Tzara’s La Fuite at the Théâtre du Vieux-Colombier to announce the birth of their poetic movement and its founding principles.

The year 1949 marked a turning point for Isou: he published a treatise on political economy titled Le soulèvement de la jeunesse (Youth Uprising) and several figures who formed what is now known as the “First Letterism” (le premier Lettrisme) joined the movement, including Jean-Louis Brau, Gil J Wolman, and Maurice Lemaître. That year Isou also published Isou ou la Mécanique des femmes (Isou or the Mechanics of Women) for which he was briefly imprisoned. The following year, a series of recitals were held at Tabou, a mythic cultural venue in Saint-Germain-des-Prés, which would be the neighborhood where the Lettrists held court and held events and activities. Isou also published Les Journaux des Dieux (The Journals of the Gods), his first “hypergraphic” novel. In 1951, Isou created his first film, Traité de bave et d’éternité (Treatise on Slime and Eternity) that caused a scandal at the Cannes Film Festival. During the festival, the young Guy Debord, future founder of the the Letterist International and, subsequently, the Situationist International, discovered Isou and his movement, and joined them briefly. Beginning in 1956, Isou developed “infinitesimal art” and, in 1959, the year Jacques Spacagna joined the movement, “aphonism.” In 1960, Isou published his second hypergraphic novel, Initiation à la haute volupté (Initiation to Exquisite Pleasure) and developed the concept of “supertemporal art.” The years 1961 and 1962 were a time of intense productivity in the visual arts for Isou; he produced nearly 200 canvases, including the Réseaux (Networks) series and created la méca-esthétique or meca-aesthetics. Roberto Altmann joined the movement, followed by Roland Sabatier in 1963 and Alain Satié in 1964, and then Jean-Pierre Gillard and François Poyet in 1966, Jean-Paul Curtay in 1967 – who, in 1974, published a collection titled La Poésie lettriste with Les Editions Seghers, and who, with Gillard, oversaw a special issue of the Revue Musicale dedicated to Letterist music in 1971 – and Broutin in 1967. The year 1968 was characterized by intense political activity and unrest of the kind Isou had foreseen in Le soulèvement de la jeunesse, and Isou spent a portion of it in a mental hospital under the care of the famous Docteur Ferdière. This became the material for Isou’s essays on psychopathology, and, later, for a third hypergraphic novel titled Jonas ou le corps à la recherche de son âme (Jonah, or the body seeking its soul), published by Broutin in 1984. In 1992, Isou published the Manifeste de l’excoordisme (Excoordist Manifesto), a new step in his theoretical thinking in which he sought to formulate a new approach to art that included and expanded beyond all other forms. In 1998, the composer and sound artist Frédéric Acquaviva sought out Isou, who by then was living alone and isolated in a small apartment, and proposed to bring his musical work back to light. Isou agreed, and in the final years of his life was extremely active musically, creating various recordings and orchestrations of earlier work, new symphonies, and discographies, published by Al Dante and £@B.

Isidore Isou died on 28 July 2007 at the age of 82.