In February 1866, three young artists tramped along the frosty paths of Fontainebleau, declaring that nature would ever be their muse. One, handsome, rich and carefree, would follow that muse until he lost everything except the respect of his friends. He died in poverty, in a home stacked with unsold paintings, while the others found success. Their names were Auguste Renoir and Claude Monet. His was Alfred Sisley, an Englishman and founding father of the Impressionist movement.

This great painter of light, described by Pissarro as an artist "of rare scope and beauty," is one of the least known Impressionists, still overshadowed by the towering reputations of his friends. So the new one-man exhibition at Isetan is an excellent chance to see Sisley's work in all its purity.

Alfred Sisley was born to English parents in France, and destined to join his father's flourishing business. However, the landscapes of Turner, Constable and Ruisdael in the National Gallery in London caught Alfred's heart and fixed his destiny. At the age of 20, he entered an artist's studio and made firm friends with students such as Renoir, Pissarro and Bazille.

But Sisley quit the studio just two years later to paint en plein air. The current Isetan exhibition, the second devoted to Sisley, starts with works from over a decade later, in 1872, when he had already discovered his clear, bright style, and ends with the final canvases of 1897.

It is not a dramatic development. Sisley had no wish to astonish or confuse: He wrote that "The viewer should be led, by the elimination of unnecessary details . . . to see at once what inspired the artist." He strove above all to capture movement, texture and life, the very "lights, dews, breezes, bloom and freshness" which Constable had pursued a generation before, declaring "not one of which has yet been perfected on the canvas of any painter in the world."

Throughout this pastoral symphony several themes are outstanding. Sisley was a great painter of water, skies and the ever-changing complexion of the weather. His skilful compositions gently lead the viewer through the scene, often by curving lanes or canals.

Consider his mastery of water. Here are rivers flowing with autumn shadows, deep and still in a spring flood, scintillating in the summer's sun, or glassy under leaden winter skies. There are many good examples, but "Le Pont de Moret en Automne" brings the shimmering water right up to the edge of the canvas until it almost spills onto our shoes. Sisley's water is so delightfully wet!

His skies reveal Ruskin's advice to artists seeking authenticity, "an earnest, faithful, loving study of nature as she really is." While some painted flat gray skies as a backdrop to the central drama of the scene, Sisley captured the sky as a living, changeful illuminator. And he gave it space to breathe. Look at his painting of the River Loing at Moret (exhibit 47). Two-thirds of the canvas is devoted to the vast and breezy heavens. The houses and narrow strip of land are just a slender bridge linking the pure elements of air and water.

In true Impressionist spirit, he would often paint the same scene under different conditions. The exhibition includes two of Sisley's 14 paintings of the old church at Moret, captured in rain and twilight. The smudgy sky and small dabs of violet, rose and white on the paving stones show his mastery of texture and admirably convey the sensation of rain. Exhibits 57 and 58 show the same view of the Bristol Channel, first with a storm brewing and then in the limpid clarity of early evening. With a minimum of fuss, he captures the dull sheen of the sea. With a minimum of strokes, he forms the mass of the cliffs, and the downward sweep of the red earth in the distance.

A few sketches remain, but mostly he painted quickly and directly onto the canvas. His paintings are peopled with boatmen, washerwomen and laborers, rapidly formed, and placed as naturally in the landscape as trees or clouds. Just one portrait by Sisley has survived, and a few still lifes. "Monet is so vast," commented Professor Nobuyuki Senzoku of Seijo University, "but Sisley wisely limited his field. His gift to us is the pure representation of the French countryside and the life of people blending with nature. He painted the Ile de France better than Monet!"

Still, his paintings did not sell. After his father's business failed in the Franco-Prussian war of 1870, Sisley fell into financial troubles from which he never recovered. Although he participated in the first and many subsequent Impressionist exhibitions, the Salon judges rejected his work, and the public scoffed. The general taste was for grandiose, narrative or sentimental paintings. Since Turner onward, painters who were trying new ways to capture nature in the raw were dismissed as "poor technicians," "lacking finish" and lathering their canvases with "soapsuds and whitewash"!

The Durand-Ruel gallery took Sisley's work to London and New York in search of buyers, but again and again they failed. Time was moving on and leaving Sisley behind. In the 1890s Gauguin sailed for Tahiti, Munch painted "The Scream" and Seurat created a sensation with the debut of Pointillism. Yet Sisley stayed true to his muse, and had no desire to exaggerate the truth of nature as he saw it.

When Sisley was in his 50s, a young friend visited his home in the small town of Moret. He was profoundly moved by the "aging artist who seemed to foresee that never, in his life, would a ray of glory shine on his art." After visiting the studio, they went to the river. "I will never forget the splendor of the trees, the light and rocks which he described so poetically, nor the life of the river people which he understood so well."

During his final trip to England in 1897 he produced the monumental pictures of the Bristol Channel and a rare and vigorous painting of the sea at Lady's Cove. Sisley had already contracted throat cancer, and after his beloved wife died he quickly deteriorated. Asking his old friend Monet to help his children, he died in January 1899, scarcely able to find 200 francs for his medicine. Monet quickly organized an auction for the benefit of Sisley's children. One canvas, originally sold for a pittance, fetched a record 43,000 francs. The painting, which Pissarro had long considered a masterpiece, is now in the Louvre.

Although his heart was in France, Sisley was a worthy successor to Constable, who asserted that "the landscape painter must walk in the fields with a humble mind. No arrogant man was ever permitted to see nature in all her beauty." Sisley himself said, "There is always a beloved nook in a painting." So take time to find it, and spare a tear for Sisley, the truest Impressionist of them all.