Politics and big science invariably mix — in the eyes of those in power, at least. Nowhere was this more true than in late-nineteenth-century France, where the radical republican government sought to identify with the rational truths of science, the prestige of national scientific discoveries and the dynamics of technological progress. Large-scale art in state buildings was a major vehicle for the promotion of this identity.

Paul-Albert Besnard's mural reflected the new age of scientific enlightenment. Credit: MAIRIE DU 1ER ARRONDISSEMENT, PARIS/LAUROS/GIRAUDON/BRIDGEMAN ART LIBRARY

The artist who succeeded most effectively in developing a new mode of painting to express this ideal was Paul-Albert Besnard (1849–1934). Now little noticed in the standard histories of French painting, he was regarded as a giant of art in his day, and was accorded the unusual accolade of a state funeral. He worked on large murals and ceiling paintings in Paris — at the Sorbonne, the School of Pharmacy and at the Hôtel de Ville (city hall).

On the ceiling of the Salle des Sciences in the Hôtel de Ville, he painted an allegory that shows how Truth, pulling the sciences in her train, pours her light on mankind. Completed in 1891, it departs radically from traditional depictions of the heavens, which were populated by gods, goddesses and symbolic figures on banks of strategically placed clouds.

Two great orbs, incompletely seen, dominate Besnard's composition. The radiant orb is the Moon, with its craters and 'seas', and the darker one is Earth. The space beyond is dense with stars and galaxies, dizzily swirling in a cosmic vortex. Truth, personified as an evanescent woman dressed in white, drags a gloomy veil — signifying obscurity — away from the sciences in her train, each crowned with laurels. The most prominent of them metaphorically points our way towards enlightenment.

Beside Truth is the phosphorescent figure of Light, ecstatically bearing a flaming sheaf of pure illumination for the benefit of mankind. A snaking parade of humans emerges from the gloom, dragged from their primitive state by what science can disclose about the world and the Universe.

All this is remote from current taste in the visual arts. We prefer to look to the Impressionists and post-Impressionists of this period; if we want an image of the heavens in painting, we are likely to describe Vincent van Gogh's The Starry Night (1889). But Besnard's depiction is highly original. He was striving to forge a new kind of symbolisme scientifique that would sweep away the old forms of classical and religious allegory.

The term 'scientific symbolism' comes from Camille Mauclair's 1914 monograph on Besnard. Mauclair defines it as “the plastic and coloristic incarnation of scientific notions in decorative allegories”. Poet, novelist, travel writer and critic, he may be taken as a spokesman for Besnard. The new form of allegory eulogizes science “not only as experimental knowledge, but also a moral doctrine, directly opposed to religious doctrine”.

Mauclair's rapturous account of the Hôtel de Ville's ceiling aims to evoke a kind of ecstasy of rational wonder, in which the sciences replace the saints as a subjects of devotion. “Here,” he exclaims, “is a hymn to fire, principle of life and of the energies of thought and understanding.” The conflagration of colours in Besnard's ceiling decoration allies the brilliance of Impressionist colour with academic draftsmanship and a dynamic of geometrical composition, in a way that Mauclair saw as ushering in the true art of the new century.

What Besnard is not doing is illustrating scientific facts. It is true that we can recognize the Moon crater Tycho, with its prominent rays, close to the contour of Earth. Large photographs of the Moon had become popular exhibits at the various universal exhibitions, not least that in Paris in 1867. And he seems to be drawing on hazy images of the nebulae. But accuracy in the literal sense is not his goal.

Besnard is creating an allegory of the spirit of science — indeed, of its spiritual dimension — one that was fitting for a new age of scientific enlightenment, in which humanity moves ever onwards and upwards towards true understanding of the cosmic mysteries. He is saying that this is the highest goal for mankind, and that a new art is needed for the brave new age.

The future for art was not to lie predominantly with Besnard. Such grandiose decorative schemes fell out of favour, as did his manner of painting, for a variety of reasons. His themes, however, as explicated by Mauclair, are still with us — science and religion, science as enlightenment and science as redeemer.