An important figure in the transitional period between impressionism and modern art,[2] he is associated with Les Nabis, symbolism, and later neo-classicism.

However, he decided to leave the school at the end of 1887 and in 1888 enrolled in Académie Julian to prepare for the entrance examination to the École des Beaux-Arts in Paris.

[8] At the Académie Julian, his fellow students included Paul Sérusier and Pierre Bonnard, who had shared ideas about painting.

In place of windows opening on nature, like the impressionists, these were surfaces which were solidly decorative, powerfully colorful, bordered with brutal strokes, partitioned.

[10] The Nabis drifted apart by the end of the 1880s, but their ideas influenced the later work of both Bonnard and Vuillard, as well as non-Nabi painters like Henri Matisse.

In November 1888 he had declared to his friend Émile Bernard that he wanted to move from "Giving color to (Puvis de Chavannes)" to "making a blend with Japan."

The celebrated opening line of the essay was: "Remember that a picture, before being a battle horse, a female nude or some sort of anecdote, is essentially a flat surface covered with colors assembled in a certain order."

With the publication of this article, Denis became the best-known spokesperson for the philosophy of the Nabis, though in fact that group was very diverse and had many different opinions about art.

She became an important part of his art, appearing in many pictures and also in decorative works, such painted fans, often as an idealized figure representing purity and love.

[14] By the early 1890s, Denis had arrived at the artistic philosophy which guided most of his later work, and which changed very little; that the essence of art was to express love and faith, which to him were similar things.

[15] On 24 March 1895 he wrote in his journal: "Art remains a sure refuge, the hope of a reason in life from now on, and the consoling thought that little beauty manifests itself in our lives, and that we are continuing the work of Creation....Therefore the work of art has merit, inscribed in the marvelous beauty of flowers, of light, in the proportion of trees and shape of waves, and the perfection of faces; to inscribe our poor and lamentable life of suffering, of hope and of thought.

In March 1891 the critic George-Albert Dourer wrote an article for the Mercure-de-France calling Denis the leading example of "symbolism in painting".

Beginning in 1889, to illustrate an edition of the book of poems Sagesse by Paul Verlaine, Denis carved a series of seven highly stylized woodblock prints, distilling the essence of his work.

Beginning in 1891, shortly after his engagement, Denis made Marthe the most frequent subject of his paintings; she was depicted, in purified and idealized form, doing household tasks, taking naps, and at the dining room table.

She appeared in his landscapes, and in his most ambitious works of the time, The series called The Muses, which he began in 1893, and showed at the Salon of Independents in 1893.

He designed a flowing lithograph, featuring Marthe, for the cover for the sheet music of La Damoiselle élue by Claude Debussy, as well as another lithograph for the poem Pelléas et Mélisande by Maurice Maeterlinck, which Debussy transformed into an opera; and in 1894 he painted La Petit Air, based on the poem Princesse Maleine by Stéphane Mallarmé, the most prominent literary proponent of symbolism.

It drew freely upon the Medici Chapel in Florence, and the works of Nicolas Poussin, Delacroix and Pierre Puvis de Chavannes.

He noted in his journal in March 1898: "Think of late paintings where Christ is the central figure...Remember the large mosaics of Rome.

Denis joined the nationalist and pro-Catholic Action Française in 1904, and remained a member until 1927, when the group had moved to the extreme right and was formally condemned by the Vatican.

[25] Until about 1906 Denis was considered in the avant-garde of Paris artists, but in that year Henri Matisse presented La Joie de Vivre with the bright and clashing colors of fauvism.

For the publisher Vollard he made a set of twelve color lithographs titled Amour, which was an artistic but not a commercial success.

He then took on a more ambitious project, the cupola for a new theater, the Théâtre des Champs-Élysées, being constructed in Paris by the architect Auguste Perret.

But his primary interestDenis responded in 1907, with the neoclassical Bacchus and Ariadne, brightening his colors and showing a happy family romping nude but more modestly on a beach.

He painted a series of works of nudes at the beach, an homage to the bathers of Raphael and the classical nudity of the Venus de Milo and other Greek sculpture.

[26] remained the painting of religious subjects, like "The dignity of labour", commissioned in 1931 by the International Federation of Christian Trade Unions to decorate the main staircase of the Centre William Rappard.

[31] On 5 February 1919, shortly after the First World War, Denis and George Desvallières founded the Ateliers d'Art Sacré, or workshops of Sacred art.

These included the ceiling over the stairway of the French Senate in the Luxembourg Palace; and murals for the Hospice of the city of Saint-Étienne, where he returned to the colorful and neoclassical themes of his beach paintings.

[36] In January 1940, in his seventieth year, he summed up his accomplishments in his journal: "My marriage: Delacroix admired and understood; Ingres abandoned; break with the extremists.

[38] The published writings and the private journal of Denis give an extensive view of his philosophy of art, which he developed over his lifetime.

In 2023 Denis' Stehender Knabe unter einem Baum, which had been listed on the German Lost Art Foundation website,[46] was found by family of Holocaust victim Marcel Monteux, from whom it had been looted.